接着上次读。
先别翻:上一站的结论是什么?自己说一遍,再继续。
翻开那一站的结论
00 / 起点与地图
不知道会发生什么,
还能不能理性地投钱?
Richard Zeckhauser 在 2006 年写了一篇不取导数、不跑回归的论文,专门讨论这个问题。他把这类情形叫 UU——未知且不可知:连有哪些未来状态都列不出来,因此也无从指派概率。这门课按他的论证顺序,一步一步把这篇 41 页的英文论文拆开读。
读完你能做的六个判断
① 给定一个投资情形,说出它属于、还是,并说出传统理论在哪一步失效。
② 判断一笔 投资为什么可能便宜:三个特征里哪些成立。
③ 判断自己有没有;没有的话,这笔能不能做成,要先确认对方哪两件事。
④ 面对「对方为什么愿意跟我成交」,算出条件期望值,判断优势倍数要多大才抵得过。
⑤ 用作者的两张格子判断自己在哪个方框,说出为什么会让正期望的投资做不成。
⑥ 复述八条格言,并各举一个原文里的例子说明它在什么条件下成立。
不教:怎么给具体资产定价、怎么做尽调、2006 年以后的市场事实、决策论与博弈论的完整证明。
路线:按依赖排,不按原文目录排
顺序与原文目录有两处不同:作者把行为经济学放在第 II 部分、把数学高手放在第 III 部分,这门课把它们分别放在站 05 与站 06,因为读到那里时你已经知道「为什么要去 UU」,才会明白这两章在防什么。
核查:这份材料的证据状态
数据截至:2006 年 9 月(论文完成) · 核查日期:2026 年 9 月 19 日
核查范围:关键数字与主要案例做了原始核查(伯克希尔 1996 年致股东信里的加州地震局条款、2006 年捐赠公告、Ricardo 滑铁卢传说的档案研究、纳斯达克跌幅、Bill Miller 连胜的结局、印度洋海啸的日期,以及三处算术的复算)。人名、机构细节、作者的课堂统计与私人通信不做外部核查,按「原文这么说」呈现。逐条记录在学习手册里。
本页是阅读工具,不是投资建议。四个可拖模型用的是论文里的例子;改动滑块只是演算,不代表任何真实资产的定价,也不构成对任何标的的判断。
下一站:把「风险」「不确定」「无知」三个词分开,看传统金融理论卡在哪一级。
01 / 风险、不确定、无知
三级阶梯:传统金融理论在哪一步失效
第 1 步有效投资的本质,是挑出「未来状态揭晓时表现好」的资产。
作者从投资这件事的定义出发:有效投资的本质,是挑出那些「当未来的状态揭晓时表现良好」的资产。这句定义里藏着一个前提——你得知道有哪些状态、每个状态的可能性有多大。如果这些概率是已知的——这正是所假设的——那么明智投资就只剩一个复杂的优化问题:在已知的收益分布上解最优权重,剩下的差别是算力、数据和执行成本。这一级作者叫。本课注这里的「风险」是技术用语,不是日常说的「危险」:一枚公平硬币的赌局风险很大,但它完全属于第一级,因为状态和概率都摆在桌面上。这一级是全文的基线——后面两级都是从这里抽掉一个东西得到的。
对照原文
The essence of effective investment is to select assets that will fare well when future states of the world become known. When the probabilities of future states of assets are known, as the efficient markets hypothesis posits, wise investing involves solving a sophisticated optimization problem. Of course, such probabilities are often unknown, banishing us from the world of the capital asset pricing model (CAPM), and thrusting us into the world of uncertainty.³
定位:第 I 节〈Escalating challenges to effective investing〉,p.4,「The essence of effective」
第 2 步概率一旦未知,我们就被逐出 CAPM 的世界,进入不确定。
作者在同一段的末尾把第一个前提抽掉:这些概率常常是未知的。前提一撤,结论也跟着撤——既然收益分布不再已知,那个「解最优权重」的优化问题就无从解起,我们被逐出 CAPM 的世界,进入,也就是 Frank Knight 1921 年给出的经典描述:概率无从知晓的情形。这里要盯住抽掉的到底是什么:只是概率。结局清单还在,你仍然说得出「通过还是不通过」「成功还是失败」,只是查不到那张概率表。本课注可以把它记成一次降级而不是崩塌:工具还能用,只是输入要靠判断而不是查表。
对照原文(本步用到的句子)
Of course, such probabilities are often unknown, banishing us from the world of the capital asset pricing model (CAPM), and thrusting us into the world of uncertainty.
定位:第 I 节〈Escalating challenges〉,p.4,「such probabilities are often unknown」
查看本段完整版(第 1 步)第 3 步如果世界主要是不确定,赢家的名单会换一批人。
作者接着做了一个推论,而这个推论决定了谁赚钱。前提是上一步的结果:概率未知,但状态已知。推演:如果金融世界主要就是这种不确定,那么最大的财务成功会归于最善于评估概率的那些人;这项技能(通常被认为属于 Bayes 决策论的领地)会盖过复杂的优化,成为可观回报的主要推手。本课注把两级放在一起看,差别就出来了:第一级比的是谁算得更好,第二级比的是谁估得更准。结论:从风险走到不确定,赢家的名单会换一批人——而下一步还要再换一次。
对照原文
Were the financial world predominantly one of mere uncertainty, the greatest financial successes would come to those individuals best able to assess probabilities. That skill, often claimed as the domain of Bayesian decision theory, would swamp sophisticated optimization as the promoter of substantial returns.
定位:第 I 节〈Escalating challenges〉,p.4,「Were the financial world」
第 4 步现实再往前一级:连有哪些状态都不知道。这是无知,作者叫它 UU。
前两级都假设你至少列得出结局清单。作者说现实的投资常常把「不知道」推进另一个维度:连可能的未来状态的身份与性质本身都不知道,因此根本没有办法明智地给这些状态指派概率。这是的世界。他给出的对照很锋利,而且是全文最重要的一句:正如传统金融理论在遇到不确定时撞墙,现代决策论在遇到无知时撞墙。本课注两堵墙的位置不同——前者失去的是分布,你还能用主观概率硬撑;后者连样本空间都没有了,主观概率无处安放,因为你不知道要给什么东西赋概率。他用缩写 指代「可能的未来状态的身份与它们的概率都未知且不可知」的情形,这就是整篇论文的对象。他在脚注里把不确定的出处交代清楚:那个经典描述来自 Frank Knight 1921 年的书。这一步的结论因此不是「UU 更难」,而是「UU 需要另一套工具」——下一步那张表就是这套工具的清单。
对照原文
The real world of investing often ratchets the level of non-knowledge into still another dimension, where even the identity and nature of possible future states are not known. This is the world of ignorance. In it, there is no way that one can sensibly assign probabilities to the unknown states of the world. Just as traditional finance theory hits the wall when it encounters uncertainty, modern decision theory hits the wall when addressing the world of ignorance. I shall employ the acronym UU to refer to situations where both the identity of possible future states of the world as well as their probabilities are unknown and unknowable. Table 1 outlines the three escalating categories; entries are explained throughout the paper.
3 The classic description of uncertainty, a situation where probabilities could not be known, is due to Frank Knight (1921).
定位:第 I 节〈Escalating challenges〉,p.4,「ratchets the level of non-knowledge」(含脚注 3 对 Knight 1921 的出处说明)
第 5 步Table 1 把三级并排:只有第三级要求互补能力与策略推断。
作者用一张表收束这一节。前提是三级的差别不只在「你知道多少」,还在「你需要什么本事」。推演按列走:第一列是你对状态的知识(概率已知 → 概率未知 → 状态未知);第二列是由此得到的投资环境(收益分布已知 → 分布靠推测 → 分布靠推测,而且常常是从对别人行为的推断中得来);第三列才是他真正要给的东西——需要的技能。风险这一级只要组合优化;不确定这一级要再加决策论;到了无知这一级,表里多出两样第一、二级没有的东西:互补能力(作者在这一格里特意加了「理想情况」四个字)与策略推断——前者是站 04 整站的主题,这里只需要先记住它出现在表里。第二列里还有一句常被略过的话:在无知这一级,互补能力常常与投资一起获得回报——也就是说,回报不是只付给钱的。本课注给一个上手的判据:判断自己在哪一级,看的是第一列「状态清单能不能列出来」;而一旦落在第三行,你要问的就不再是「我的模型够不够好」,而是「我有没有别人没有的能力」和「我能不能推断出别人在想什么」。这一格是后面站 04 与站 08 的种子。
对照原文
Table 1. Escalating Challenges to Effective Investing
| | Knowledge of States of the World | Investment Environment | Skills Needed | |---|---|---|---| | Risk | Probabilities known | Distributions of returns known | Portfolio optimization | | Uncertainty U | Probabilities unknown | Distributions of returns conjectured | Portfolio optimization, Decision theory | | Ignorance UU | States of the world unknown | Distributions of returns conjectured, often from deductions about other’s behavior. Complementary skills often rewarded along side investment | Portfolio optimization. Decision theory. Complementary skills (ideal) Strategic inference. |
定位:第 I 节,p.5,「Escalating Challenges to Effective」
三级阶梯对照(Table 1)
| 你对未来状态知道什么 | 投资环境 | 需要的技能 | |
|---|---|---|---|
| 风险 Risk | 概率已知 Probabilities known | 收益分布已知 Distributions of returns known | 组合优化 Portfolio optimization |
| 不确定 Uncertainty · U | 概率未知 Probabilities unknown | 收益分布靠推测 Distributions of returns conjectured | 组合优化+决策论 Portfolio optimization, Decision theory |
| 无知 Ignorance · UU | 连状态本身都未知 States of the world unknown | 收益分布靠推测,而且常常是从对别人行为的推断中得来;互补能力常与投资一起获得回报 …often from deductions about other’s behavior. Complementary skills often rewarded along side investment | 组合优化。决策论。互补能力(理想情况)。策略推断。 …Complementary skills (ideal) Strategic inference. |
读表最快的办法:从上往下看第一列,问自己「我列得出结局清单吗?列得出的话,概率查得到吗?」两个都答不上,就在第三行。
这一站的结论
概率已知时,明智投资是一个优化问题;概率未知时,估概率的能力压过优化;连状态都未知时,前两样都不够,还需要互补能力(理想情况)与对他人行为的策略推断。
本课注配套的上手判据:判断自己在哪一级,看的是「状态清单能不能列出来」,不是波动有多大。
想一想:「明年某国会不会通过某项法案」和「十年后哪种技术会主导支付」,这两个情形分别落在三级阶梯的哪一级?分界卡在哪个环节上?
写下你的答案再展开
前者是不确定:结局清单清楚(通过/不通过/搁置),只是概率查不到表。后者是无知:十年后的支付方式可能包含今天还没有名字的东西,你连状态清单都列不全。分界卡在「状态的身份与性质是否已知」这一环,不在概率的精确度上——这正是本站第 4 步里作者把两堵墙分开的地方。
下一站:作者据此给出两个坏结论和两个好结论,并说明不可知事件通常长什么样。
02 / 四个结论与事件的样子
UU 世界的四个结论,和不可知事件的样子
第 1 步第一个坏结论:不可知情形普遍且不可避免——总体的和个体的都算。
作者从「无知是不是少见的例外」这个问题出发。他的推演分两层:先举总体层面的例子,全球变暖对金融市场的后果、未来的恐怖活动、最有前途的技术——这些今天的不可知,正如 1997 年亚洲金融危机、9/11、世纪之交纳斯达克的暴涨暴跌在发生前一样不可知;再指出更重要的一层:许多不可知是个体的、特异的,只影响一个人或几个人——「我在城西十英里外建三百户社区,人会来吗?」「越南政府会不会让我大规模销售这个保险产品?」「我朋友的新软件会不会抓住大众的兴趣,如果不会,它会不会在一个完全不同的应用上成功?」结论是:这类个体的 UU 情形,恰恰蕴含最大的超额回报潜力。
对照原文
This essay has both dreary and positive conclusions about investing in a UU world. The first dreary conclusion is that unknowable situations are widespread and inevitable. Consider the consequences for financial markets of global warming, future terrorist activities, or the most promising future technologies. These outcomes are as unknowable today as were the 1997 Asian meltdown, the 9/11 attacks, or the NASDAQ soar and swoon at the end of the century, shortly before they were experienced.
These were all aggregate unknowables, affecting a broad swath of investors. But many unknowables are idiosyncratic or personal, affecting only individuals or handfuls of people, such as: If I build a 300-home community ten miles to the west of the city, will they come? Will the Vietnamese government let me sell my insurance product on a widespread basis? Will my friend’s new software program capture the public fancy, or if not might it succeed in a completely different application? Such idiosyncratic UU situations, I argue below, present the greatest potential for significant excess investment returns.
定位:第 I 节,p.5,「both dreary and positive conclusions」
第 2 步第二个坏结论:多数投资者的训练来自另一个世界,认出不可知就躲,躲不掉就出错。
前提是上一步的结论——不可知无处不在。作者接着问:投资者准备好了吗?他的判断是没有:多数投资者受的训练(如果有的话)适用于「状态与概率都假设已知」的世界,面对不可知根本不知道该怎么办。他们一旦认出不可知,倾向于避而远之,而且常常是为了保护自己不被别人事后狙击。但作者立刻补一句限定:除了最简单的投资之外,卷进去是不可避免的——而一旦卷进去,他们就会犯严重的错误。于是坏消息是双份的:机会常在,但多数人既躲不开也处理不好。
对照原文
The second dreary conclusion is that most investors – whose training, if any, fits a world where states and probabilities are assumed known – have little idea of how to deal with the unknowable. When they recognize its presence, they tend to steer clear, often to protect themselves from sniping by others. But for all but the simplest investments, entanglement is inevitable – and when investors do get entangled they tend to make significant errors.
定位:第 I 节,p.6,「The second dreary conclusion」
第 3 步不可知事件有两种样子:晴天霹雳和缓慢漂移;两种事后看都不再奇怪。
作者先描述第一种:许多不可知事件以毫无预兆的雷声到来,几乎不留时间准备;但一旦发生,它们看上去就不那么奇怪了。人脑有惊人的能力为「本该预见到 9/11」或者亚洲的两场海啸找出事后的理由——他把这两场分别归因于货币崩溃与海底地震。这种把后见之明写进记忆的倾向,在有人准备事后指责我们时尤其强烈,它妨碍我们预见未来的极端事件,也让我们从自己的误估中学不到东西。第二种是缓慢漂移:苏联解体是这样,多数股市波动也是这样——他举纳斯达克 1996 年 1 月起四年涨五倍、随后三年跌掉三分之二为例,说这不像雷声,更像先把气球吹起来再慢慢放气。作者在这里加了一句自己的限定:这类长期单向运动本不该发生——如果价格随时反映全部相关信息,连续的意外好消息或坏消息就该极其罕见。他还补了一个同类的例子:艾滋病如今看来是熟悉的领域,但 25 年前全美累计只有 31 例死亡时,没有人会预测出一场杀死数千万人的全球流行病。
对照原文
Many of the events that we classify as unknowable arrive in an unanticipated thunderclap, giving us little or no time to anticipate or prepare. But once they happen, they do not appear that strange. The human mind has an incredible ability to find a rationalization for why it should have been able to conjecture the terror attack of 9/11; or the Asian tsunamis of 1997 and 2005, respectively caused by currency collapse and underwater earthquake. This propensity to incorporate hindsight into our memories – and to do so particularly when Monday morning quarterbacks may attack us – hinders our ability to anticipate extreme events in the future. We learn insufficiently from our misestimates and mistaken decisions.
Other unknowable events occur over a period of time, as did the collapse of the Soviet Union. Consider most stock market swings. Starting in January 1996, the NASDAQ rose five-fold in four years. Then it reversed field and fell by two thirds in three years. Such developments are hardly thunderclaps. They are more like blowing up a balloon and then dribbling out the air. In retrospect, these remarkable swings have lost the flavor of an unknowable event, even though financial markets are not supposed to work that way. If securities prices at any moment incorporate all relevant information, a property that is usually posited, long-term movements in one direction are hardly possible, since strong runs of unanticipated good news or bad news will be exceedingly rare. Similarly, the AIDS scourge now seems familiar territory, though 25 years ago – when there had been only 31 cumulative deaths in the U.S. from AIDS – no one would have predicted a world-wide epidemic killing tens of millions and vastly disrupting the economies of many poor nations.
定位:第 I 节〈The nature of unknowable events〉,p.6–7,「unanticipated thunderclap」
纠错:原文写「the Asian tsunamis of 1997 and 2005」;由海底地震引发的那场海啸发生在 2004 年 12 月 26 日(印度洋,震级约 9.1 级,约 22.8 万人罹难),修正为 2004 年。作者用这个例子说明「事后看不再奇怪」,论点不受影响。
核查:纳斯达克的涨幅与原文一致(1996 年初约 1030 点涨到 2000 年 3 月 10 日收盘 5048.62,约 4.9 倍);跌幅原始数据为跌到 2002 年 10 月 9 日收盘 1114.11,约 −78%、用时约两年半,比原文写的「三年跌掉三分之二」更陡也更快。
第 4 步上行的不可知事件更难被识别,所以我们高估了「意外都是坏的」。
作者从 Buffett 1996 年的一句话出发:「必须记住,几乎所有的意外都是不愉快的。」然后他提出这可能更多是感知问题而非事实:上行的不可知事件——比如恐袭减少、或者从绝症中康复——本身就难以辨认。任何单独一天发生袭击本来就不太可能,而病人在康复路上仍然觉得难受;消息是一点一点渗进来的,像金融市场的上涨一样。他借 B. F. Skinner 的发现加一层解释:由变间隔强化塑造的行为最难消退,因为受试者永远无法确定下一次奖励不会来;同样地,当一串间隔不定的事件其实已经结束时,我们很难察觉——如果那些事件是不愉快的,我们也就不知道该在什么时候庆祝它们的终结。接着他把镜头单独对准晴天霹雳那一类:这类事件之所以配得上这个名字,就是因为它出格——好的坏的都算。但他说,随便看看本地、全国和国际的头条就会发现,晴天霹雳不成比例地是坏事:不像老电视剧《The Millionaire》里那样,不会有人敲你的门送来一船钱;而在伊拉克,恐怖袭击的次数远远多于抓获恐怖分子的次数。作者的结论:金融领域可能是上下行比例相对好的一个地方,尤其把漂移型事件也算进来。他给的一个旁证是,到 2004 年底美国有 250 万百万富翁(不含房产财富),其中许多人无疑经历过上行的不可知事件。
对照原文
Are UU events to be feared? Warren Buffett (1996) once remarked: “It is essential to remember that virtually all surprises are unpleasant.” Most salient UU events seem to fall into the left tail of unfortunate occurrences. This may be more a matter of perception than reality. Often an upside unknowable event, say the diminution of terror attacks or recovery from a dread disease, is difficult to recognize. An attack on any single day was not likely anyway, and the patient still feels lousy on the road to recovery. Thus, the news just dribbles in, as in a financial market upswing. B.F. Skinner, the great behavioral psychologist, taught us that behavior conditioned by variable interval reinforcement – engage in the behavior and from time-to-time the system will be primed to give you a payoff – was the most difficult to extinguish. Subjects could never be sure that another reward would not be forthcoming. Similarly, it is hard to discern when a string of inconsistently spaced episodic events has concluded. If the events are unpleasant, it is not clear when to celebrate their end.
Let us focus for the moment on thunderclap events. They would not get this title unless they involved something out of the ordinary, either good or bad. Casual empiricism – judged by looking at local, national and international headlines – suggests that thunderclap events are disproportionately adverse. Unlike in the old television show, The Millionaire, people do not knock on your door to give you a boatload of money, and in Iraq terror attacks outnumber terrorist arrests manifold.
The financial arena may be one place with an apparently good ratio of upside to downside UU events, particularly if we include events that are drifts and not thunderclaps. By the end of 2004, there were 2.5 million millionaires in the United States, excluding housingwealth. http://money.cnn.com/2005/06/09/news/world_wealth/ Many of these individuals, no doubt, experienced upside UU events. Some events, such as the sustained boom in housing prices, were experienced by many, but many upside events probably only affected the individual and perhaps a few others; such events include an unexpected lucrative job, or having a business concept take a surprisingly prosperous turn, or having a low-value real estate holding explode in value, etc.
定位:第 I 节〈The nature of unknowable events〉,p.7,「Are UU events to be feared」
第 5 步两个好结论:不可知伴随极高回报,而且有系统方法——代价是必须接受事后看很蠢的投资。
前提是前面两个坏结论。作者的转折是:第一,不可知情形过去与未来都伴随着极其强劲的投资回报;第二,存在系统化的思考方式,照做就能通向超常的期望回报。他立刻自己加限定:一些重大亏损不可避免,其中一些事后看会显得该被责备;但净的期望结果,即使计入风险厌恶,仍然强烈为正。然后是全文最有名的一句提醒:如果是你的首要顾虑,就别往下读了。他给的类比是:在一个不可知的世界里,如果你的桥一座都没塌,说明你把桥造得太结实了;同样地,如果你的投资事后看没有一笔显得愚蠢,说明你离不可知太远。紧接着他给出与这条提醒配对的训练法:Buffett——他称之为投资不可知的大师,也因此是本文的主角——常说打桥牌是最好的商业训练。桥牌要求你在顶多算勉强可知的局面里持续评估概率,一局之内要做几百个决策,而且往往要在期望收益与期望损失之间权衡。但作者强调真正关键的是另一件事:牌手还必须不断与「好决策带来坏结果」讲和——既包括自己的决策,也包括搭档的。要在一个不可知的世界里明智地投资,需要的正是这种讲和的本事。
对照原文
The first positive conclusion is that unknowable situations have been and will be associated with remarkably powerful investment returns. The second positive conclusion is that there are systematic ways to think about unknowable situations. If these ways are followed, they can provide a path to extraordinary expected investment returns. To be sure, some substantial losses are inevitable, and some will be blameworthy after the fact. But the net expected results, even after allowing for risk aversion, will be strongly positive.
Do not read on, however, if blame aversion is a prime concern: The world of UU is not for you. Consider this analogy. If in an unknowable world none of your bridges fall down, you are building them too strong. Similarly, if in an unknowable world none of your investment looks foolish after the fact, you are staying too far away from the unknowable.
Warren Buffett, a master at investing in the unknowable, and therefore a featured player in this essay, is fond of saying that playing contract bridge is the best training for business. Bridge requires a continual effort to assess probabilities in at best marginally knowable situations, and players need to make hundreds of decisions in a single session, often balancing expected gains and losses. But players must also continually make peace with good decisions that lead to bad outcomes, both one’s own decisions and those of a partner. Just this peacemaking skill is required if one is to invest wisely in an unknowable world.
定位:第 I 节,p.6,「The first positive conclusion」
两种不可知事件的对照
| 晴天霹雳(thunderclap) | 缓慢漂移(drift) | |
|---|---|---|
| 怎么到来 | 毫无预兆,几乎不留准备时间 | 一点一点渗进来,像给气球放气 |
| 原文的例子 | 9/11;海底地震引发的海啸;1987 年 10 月一天跌 20% | 苏联解体;纳斯达克四年涨五倍再大幅回落;艾滋病从 31 例到全球流行 |
| 事后怎么被讲述 | 人脑迅速编出「本该预见」的理由 | 看起来不再像不可知,尽管市场本不该这样运动 |
| 对投资者的含义 | 高估自己的预见力,从误估中学不到东西 | 难以判断一串事件何时结束,上行的尤其难识别 |
读表最快的办法:先看最后一行。两类事件造成的错误不同——霹雳让你高估自己,漂移让你分不清结束没有。
这一站的结论
不可知不是可以回避的例外,而是常态,个体层面的尤其多;多数投资者既躲不开也处理不好。好消息是这类情形伴随极高回报且有系统方法可循,净期望即使计入风险厌恶也强烈为正。代价是你必须接受:总有几笔事后看起来很蠢。
边界:这一站哪些话不能当成统计结论
- 「净期望强烈为正」是作者的判断,全文没有给出样本、期间或收益分母,也没有做检验;他自己在结论一节说,本文提供的是猜想与轶事,不是确定的数据。
- 「桥不塌说明造得太结实」是类比,用来说明「事后看蠢的投资是必要成本」,不能反过来当成「亏了就说明做对了」。
- 2004 年底 250 万百万富翁这个数字来自当年的财富报告,作者引用的原始链接今天已失效,本课未做原始核对。
下一站:这些机会为什么会便宜到值得买——唯一性、厚尾,以及必须同时成立的三个特征。
03 / 唯一性、厚尾与三特征
UU 为什么会便宜:唯一性、厚尾与三个特征
第 1 步第三个 U 是 unique:一次性的事情会赶走套利者,也赶走怕被追责的人。
作者从「谁会来跟你抢」这个问题出发。他说许多 UU 情形还配得上第三个 U——。推演分两条:套利者喜欢有大量过往经验作参照,一次性的局面里没有这种参照,他们会避开;任何会因为事后被判定决策糟糕而受重罚的人,也会避开。两类人一起退场,结论就是:缺少来自精明且有钱的对手的竞争,意味着你有机会买到定价过低的证券。
对照原文
Many UU situations deserve a third U, for unique. If they do, arbitrageurs – who like to have considerable past experience to guide them – will steer clear. So too will anybody who would be severely penalized for a poor decision after the fact. An absence of competition from sophisticated and well-monied others spells the opportunity to buy underpriced securities.
定位:第 I 节〈Uniqueness〉,p.9,「deserve a third U, for unique」
第 2 步这就是猜想 1:UUU 把投机者赶走,从而造成有吸引力的低价。
作者先给证据再给命题。证据是:从 Ricardo 到 Buffett,最伟大的投资者大多把大部分财富押在 UUU 局面上赚到。他说 Ricardo 据说在滑铁卢债券上赚了 100 万英镑(约合今天 5000 万美元),大约是他去世时财产的一半;Buffett 做过几十笔同量级的投资。这里作者特意做了一个对比,值得停一下:人们熟知的 Buffett 是内布拉斯加家具城和喜诗糖果的买家,或者华盛顿邮报与可口可乐的长期持有者——这些都是可以做传统分析的生意;但多年来伯克希尔真正的财富消防水管是保险,而保险常常需要 UUU 式的思考。换句话说,让他出名的那部分和让他变富的那部分不是同一部分。他还预告了后面第 V 节的那个案例:许多专家把它看成 UUU 局面因而避开,Buffett 却看出保费相对风险有超额空间,于是整层吃下。把证据收拢,他把这条写成编号命题:——UUU 投资赶走投机者,从而创造出一个有吸引力的低价的可能。注意「可能」两个字:作者写的是 potential,不是保证。
对照原文
Most great investors, from David Ricardo to Warren Buffett, have made most of their fortunes by betting on UUU situations. Ricardo allegedly made 1 million pounds (over $50 million today) – roughly half of his fortune at death – on his Waterloo bonds.⁵ Buffett has made dozens of equivalent investments. Though he is best known for the Nebraska Furniture Mart and See’s Candies, or for long-term investments in companies like the Washington Post and Coca Cola, insurance has been Berkshire Hathaway’s firehose of wealth over the years. And insurance often requires UUU thinking. A whole section below discusses Buffett’s success with what many experts saw as a UUU insurance situation, so they steered clear; but he saw it as offering excess premium relative to risk, so he took it all.
Speculation 1: UUU investments – unknown, unknowable and unique – drive off speculators, which creates the potential for an attractive low price.
定位:第 I 节〈Uniqueness〉,p.9,「Most great investors」
核查:「Ricardo 赚了 100 万英镑」原文已用 allegedly(据说)留了余地。原始档案研究(Parys,《剑桥经济学杂志》2024 年)认为这个数字出自关于 Ricardo 或 Rothschild 的不可靠传说;1815 年那笔国债确实给他带来可观利润,但他的财富主要来自长期做市与七次英国国债承销的小幅利润累积。
第 3 步但唯一性会被重复消解:看着独特的局面,见得多了就变成可投机的类别。
作者自己给这条猜想加限定,前提是「唯一」是个经验判断而不是本质属性。他举收购要约:一家公司对另一家出价时,常常无法判断在发生什么、会发生什么,看上去很唯一;但这类事情这些年见过几十上百次,投机者愿意在其中建仓。于是从投资的角度看,唯一性消失了。他的比喻很干脆:每个孩子都是独一无二的,这件事对造球鞋的人来说无关紧要。本课注由此得到一个可以直接用的判据:判断「唯一」要看有没有可供投机者参照的同类样本,不是看这件事听起来多稀奇。
对照原文
Some UU situations that appear to be unique are not, and thus fall into categories that lend themselves to traditional speculation. Corporate takeover bids are such situations. When one company makes a bid for another, it is often
impossible to determine what is going on or what will happen, suggesting uniqueness. But since dozens of such situations have been seen over the years, speculators are willing to take positions in them. From the standpoint of investment, uniqueness is lost, just as the uniqueness of each child matters not to those who manufacture sneakers.
定位:第 I 节〈Uniqueness〉,p.9–10,「appear to be unique are not」
第 4 步回报为什么可能极端:尾部比钟形曲线厚得多。
前提是「低价」只有配上「大回报」才值得追。作者说 UUU 投资的回报可以非常极端。他先拆掉默认工具:钟形曲线很好地描述了大量投掷公平硬币出现正面的次数,但这种机械且受控的问题极其罕见;身高常被说成服从钟形曲线,实际上极高和极矮的人都太多了,原因可能是腺体紊乱或基因异常——标准模型在尾部常常不适用。投资受到的扰动也一样:不管 1987 年 10 月那次崩盘的解释是什么,都不是通常用来解释市场波动的那些因素。更一般地,金融市场与各类投资的波动看起来有远比布朗运动所预测的更。他给出两种可能的原因:底层因素本身就产生厚尾,或者存在罕见的、反常的、「怪」的原因产生极端结果,或者两者兼有;而 UU 与 UUU 模型更倾向于后一种解释。脚注里他提到 Taleb 与 Mandelbrot 主张许多金融现象服从。
对照原文
The returns to UUU investments can be extreme. We are all familiar with the Bell Curve (or Normal Distribution), which nicely describes the number of flips of a fair coin that will come up heads in a large number of trials. But such a mechanical and controlled problem is extremely rare. Heights are frequently described as falling on a Bell Curve. But in fact there are many too many people who are extremely tall or extremely short, due say to glandular disturbances or genetic abnormalities. The standard model often does not apply to observations in the tails. So too with most disturbances to investments. Whatever the explanation for the October 1987 crash, it was not due to the usual factors that are used to explain market movements.⁶
More generally, movements in financial markets and of investments in general appear to have much thicker tails than would be predicted by Brownian motion, the instantaneous source of Bell Curve outcomes. That may be because the fundamental underlying factors produce thicker tails, or because there are rarely occurring anomalous or weird causes that produce extreme results, or both. The UU and UUU models would give great credence to the latter explanation, though both could apply.⁷
定位:第 I 节〈Weird Causes and Fat Tails〉,p.10,「The returns to UUU investments can be extreme」
第 5 步价格按比例而非绝对量对称,所以大波动既是敌也是友。
作者在这里做了一段可以复算的推演。前提是价格不可能为负,因此若价格以某种对称方式运动,这种对称必须按来衡量。推演:如果变动相对于均值很小,比例与绝对量几乎没有差别——价格 100 每年平均上下 3,也就是乘 103/100 或乘 100/103,差别无关紧要;但把 3 换成 50,百分比对称就帮上大忙了:价格变成 100×(150/100) 或 100×(100/150)。结论是:如果价格接近百分比对称——许多人相信是这样——那么大幅波动既是敌人也是朋友:敌人是因为它带来大风险,朋友是因为它提供可观的正期望值。作者接着把这层意思推到极端:许多百万富翁的投资翻了 10 倍,有些翻了 100 倍;对称的几何模型会认为「本金缩到十分之一或百分之一」同样可能,而「以同样的频率拿到 10 倍或 100 倍、或者几乎全亏」这个赌局极具吸引力。
对照原文
While still in this Pollyannish frame, it is worth noting the miracles of percentage symmetry given extreme events. Posit that financial prices move in some symmetric fashion. Given that negative prices are not possible, such changes must be in percentage rather than absolute terms.⁴ We will not notice any difference between percentage and absolute if changes are small relative to the mean. Thus, if a price of 100 goes up or down by an average of 3 each year, or up by a ratio of 103/100 or down by 100/103 hardly matters. But change that 3 to a 50, and the percentage symmetry helps a great deal. The price becomes 100(150/100) or 100(100/150)), which has an average of 117. If prices are anything close to percentage symmetric, as many believe they are, then big swings are both enemy and friend: enemy because they impose big risks, friend because they offer substantial positive expected value.
Many millionaires have made investments that multiplied their money 10-fold, and some 100-fold. The symmetric geometric model would expect events that cut one’s stake to 1/10th or 1/100th of its initial value to be equally likely. The opportunity to get a 10 or 100 multiple on your investment as often as you lose virtually all of it is tremendously attractive.
定位:第 I 节,p.8,「miracles of percentage symmetry」
纠错:原文把 100×(150/100) 与 100×(100/150) 的平均写成 117;按作者自己给的这两个结果(150 与 66.7)复算,算术平均是 108.3。同一算法用在他的 ±3 例子上得 100.04,与他说的「几乎无关紧要」一致,可见算法本身没问题。论点不受影响:108.3 仍高于基准 100。
第 6 步三个特征同时成立时,超额回报才值得期待。
作者在这里收口,并且先把话说回来:没有任何理由要求投资一定给出对称的几何回报。但他说,如果一笔投资具备本文讨论的三个特征,看不到显著的期望超额回报反而才奇怪。三个特征是:(1) 底层具有 UU 属性;(2) 需要互补能力才能进行,因而这笔投资不对一般市场开放;(3) 交易对手方不太可能比你更知情。他随即加限定:这种三管齐下的机会不会天天出现,而且出现时往往无法按投资者希望的规模放大——不像一只被低估的纽约交易所股票那样,至少在个人投资者的规模区间里可以顺畅加仓。结论因此带一条行动含义:对 UU 敏感的投资者必须持续搜寻新机会——这正是 Buffett 在每份伯克希尔年报里征购新生意、以及多数富有的私人投资者不断寻找新工具与新交易的原因。
对照原文
There is, of course, no reason why investments must yield symmetric geometric returns. But it would be surprising not to see significant expected excess returns to investments that have three characteristics addressed in this essay: (1) UU underlying features, (2) complementary capabilities are required to
undertake them, so the investments are not available to the general market, and (3) it is unlikely that a party on the other side of the transaction is better informed. That is, UU may well work for you, if you can identify general characteristics of when such investments are desirable, and when not.
These very attractive three-pronged investments will not come along everyday. And when they do, they are unlikely to scale up as much as the investor would like, unlike an investment in an underpriced NYSE stock, which scales nicely, at least over the range for most individual investors. Thus, the UU-sensitive investor should be constantly on the lookout for new opportunities. That is why Warren Buffett trolls for new businesses to buy in each Berkshire-Hathaway annual report, and why most wealthy private investors are constantly looking for new instruments or new deals.
定位:第 I 节,p.8–9,「three characteristics addressed in this essay」
试一试:把年波动从 3 拖到 50,看平均落在哪里
这里配可拖模型,是因为作者用两个数字(3 与 50)说明一条凸曲线,而凸性恰恰是文字最难说清的东西。拖动之前先回答:当波动很小的时候,「按比例对称」和「按绝对量对称」的差别应该接近多少?
基准价固定为 100,与原文的例子一致。百分比对称是一个比例现象:换一个基准价,上下两个结果与平均值都会等比例缩放,曲线的形状不变,所以这里只留下一个真正会改变结论的变量。
上下两个结果的算术平均
读图:横轴是年波动比例 g(0 到 100%),纵轴是 P(1+g) 与 P/(1+g) 的算术平均,与基准价同单位。基准是当前的 P 本身——曲线高出基准多少,就是百分比对称带来的那部分正期望值。
想一想:你手上正在看的那个机会,凭什么认为它便宜?把这两个问题分开答:①「唯一性」还在不在——这类局面过去几年出现过几十次吗,有没有人已经把它做成了可投机的类别?②「价格低」是你观察到的,还是你从「别人都不碰」推出来的?
写下你的答案再展开
作者只在两件事同时成立时才说价格会低:唯一性把套利者与怕被追责的人赶走(第 1–2 步),而且这件事没有被重复消解成一个可投机的类别(第 3 步)。收购要约就是被消解掉的例子——单看每一笔都独特,见得多了投机者就愿意进场,唯一性从投资角度消失了。第二个问题更要紧:猜想 1 说的是 UUU「创造出低价的可能」(potential),不是保证低价。「别人都不碰」既可能因为他们被模糊厌恶挡住(站 05),也可能因为他们看到了你没看到的东西(站 08 的 E 格)。所以这一步的正确动作不是假定便宜,而是回到第 6 步的三个特征逐条核对——尤其是第三条:对手方是不是真的不太可能更知情。
这一站的结论
唯一性把套利者和怕被事后追责的人一起赶走,剩下稀薄的竞争和偏低的价格(猜想 1);回报之所以可能极端,是因为尾部比钟形曲线厚得多,而价格的百分比对称让大波动同时带来大风险和正的期望值。但值得期待超额回报的,只有三个特征同时成立的那一类机会,而且它们既稀少又不易放大规模。
下一站:三个特征里的第二个——互补能力——本身就是一整套方法,也是作者给普通人的那条路。
04 / 互补能力与挎斗投资
互补能力与挎斗投资:你凭什么拿得到
第 1 步UU 投资的超额回报大多付给与资本互补的稀缺能力,不是付给资本。
作者的前提是站 03 的第二个特征。他把它展开成一条观察:很大比例的 UU 投资、以及更大比例的 UUU 投资,回报都付给了一项。第一个例子是房地产:近年美国的许多巨额财富来自这里,而这些回报归于那些知道在哪儿建、建什么、怎么建的人——开发商在自己的资本上赚到巨额回报,是因为他们有互补能力。第二个例子是风险投资人:他们能在自有资金上获得非凡回报,并向自己的出资人收取可观费用,因为早期公司需要他们的技能与人脉。第三个例子是高科技先驱,Bill Gates 是极端的一个,他们的每一块投资美元拿到的倍数更高,因为资本是在补足他们的远见与科学洞察。结论:这类投资的回报来自「稀缺能力」与「明智选择标的」的组合,不是来自钱本身。
对照原文
A great percentage of UU investments, and a greater percentage of those that are UUU, provide great returns to a complementary skill. For example, many of America’s great fortunes in recent years have come from real estate. These returns came to people who knew where to build, and what and how. Real estate developers earn vast amounts on their
capital because they have complementary skills. Venture capitalists can secure extraordinary returns on their own monies, and charge impressive fees to their investors, because early stage companies need their skills and their connections. In short, the return to these investments comes from the combination of scarce skills and wise selection of companies for investment. High tech pioneers – Bill Gates is an extreme example – get even better multiples on their investment dollars as a complement to their vision and scientific insight.⁸
定位:第 I 节〈Complementary skills and UU investments〉,p.10–11,「returns to a complementary skill」
第 2 步普通股票投资里的理想互补能力是「不寻常的判断力」。
作者先承认限制:我们中很少有人具备做开发商、风投或高科技先驱的本事。那么能不能在普通的股票投资里当明星?他说这类努力的理想互补能力是不寻常的判断力——能够明智地决定何时投入、何时避开 UUU 投资的人会拿到显著优势,因为这里的错误定价往往很严重。他的例子是 Legg Mason Value Fund 的 Bill Miller:到 2005 年 12 月为止连续 15 年跑赢标普,这是独一无二的记录。2004 年 10 月 Miller 在哈佛详细解释了他为什么在 Google 上市时大举买入——考虑到这家公司的性质,以及它是通过荷兰式拍卖发行的,那无疑是一个 UUU 局面。当时在场的人几乎都对这个决定印象深刻:股票当年 8 月以 85 美元发行,已经涨到 140 美元。但作者指出 Miller 自己明白,解释过去的成功并不难;他接着宣告 Google 未来也是好投资——而到本文完稿的 2006 年 9 月,Google 报 380 美元。作者随即自己加了限定:2006 年对 Miller 并不友好,到 9 月他的基金全年落后标普 12%,「只有时间能说明他是失去了手感,还是仅仅处在低潮」。
对照原文
Alas, few of us possess the skills to be a real estate developer, venture capitalist or high tech pioneer. But how about becoming a star of ordinary stock investment? For such efforts an ideal complementary skill is unusual judgment. Those who can sensibly determine when to plunge into and when to refrain from UUU investments gain a substantial edge, since mispricing is likely to be severe. Bill Miller, the famed manager of the Legg Mason Value Fund, had a unique record of beating the S&P; his string through December 2005 was 15 years in a row. In October 2004 he spoke at Harvard University, and explained in detail why he made major purchases of Google at its public offering, surely a UUU situation given the nature of the company and the fact that it was offered through a Dutch auction.⁹ Virtually all in the audience were impressed that he made this decision -- the stock came out at $85 in August that year and had run up to $140. But Miller recognized that explaining past successes is not a challenge. He went on to proclaim Google a great investment for the future. How right he was. Google was selling at $380 in September 2006, when this essay was completed. Alas, 2006 was not kind to Miller. By September, his Value Fund was 12% behind the S&P for the year. Only time will tell whether Miller has lost his touch or is merely in a slump.
定位:第 I 节〈Complementary skills〉,p.11,「an ideal complementary skill is unusual judgment」
核查:原文写作时结果未定。原始记录显示:Miller 的连胜是 1991 至 2005 年共 15 年,2006 年全年 Value Trust 落后标普,连胜就此终结。这是论文完稿之后的结果,不是原文的错误。
第 3 步Buffett 的互补能力让公司主动找上门,而且常常给他折价。
作者用 Buffett 作对照。前提是互补能力未必是技术性的。Buffett 的不寻常判断力用在更平凡的公司上,比如石油生产商和软饮料企业;他只是在日常任务上是天才——判断管理层能力、预测公司进展——他把判断一家公司未来时的那部分不可知给排掉了很多。但作者说他还有别的优势:一些投资是公司主动找上门的,请他投资并进入董事会,看重的是他的审慎、他的老练、他正直的声誉——也就是他的互补能力,而不只是他的钱。结论落在价格上:当他因为这些原因被请来时,他常常拿到折价。
对照原文
Warren Buffett’s unusual judgment operates with more prosaic companies, such as oil producers and soft drink firms. He is simply a genius at everyday tasks, such as judging management capability or forecasting company progress. He drains much of the unknowable in judging a company’s future. But he has other advantages. A number of Buffett’s investments have come to him because companies sought him out, asking him to make an investment and also to serve on their board, valuing his discretion, his savvy, and his reputation for rectitude – that is, his complementary skills, not merely his money. And when he is called on for such reasons, he often gets a discounted price. Those like Miller
定位:第 I 节〈Complementary skills〉,p.11,「unusual judgment operates with more prosaic companies」
第 4 步但结论不是模仿他们:缺这种能力去当大胆选股人会被吃掉。
作者在这里做了一个关键的转折,前提是上两步的能力是不可复制的。他说,像 Miller 和 Buffett 这样能在股票市场投资中运用互补能力的人,会处在竞争有限的特权位置;但如果他们不拿出勇气、不在预期高回报的地方大举买入,这个位置也没什么用。接着是给读者的那句:对普通人而言,教训不是去模仿他们,那和试图像费德勒一样打网球没有区别——他们每个人都有无法复制的能力。结论很直白:如果你不具备 Buffett–Miller 那样的能力,去当一个大胆的选股人会被嚼碎。作者随后补了一层解释:大投资者乐于公开自己的成功(Buffett 在年报里,Miller 在哈佛,还有大量来给 MBA 讲课的风投),正是因为少有人具备同类的互补能力,他们不必担心竞争。
对照原文
and Buffet, who can leverage complementary skills in stock market investment, will be in a privileged position of limited competition. But that will accomplish little if they do not show courage and make big purchases where they expect high payoffs. But the lesson for regular mortals is not to imitate Warren Buffett or Bill Miller; that makes no more sense than trying to play tennis like Roger Federer. Each of them has an inimitable skill. If you lack Buffett-Miller capabilities, you will get chewed up as a bold stock picker.
Note, by the way, the generosity with which great investors with complementary skills explain their successes – Buffett in his annual reports, Miller at Harvard, and any number of venture capitalists who come to lecture to MBAs. These master investors need not worry about the competition, since few others possess the complementary skills for their types of investments. Few UU investment successes come from catching a secret, such as the whispered hint of “plastics” in the movie The Graduate. Mayer Amschel Rothschild had five sons who were bright, disciplined, loyal and willing to disperse. These were the complementary skills. The terrific investments in a UU world – and the Rothschild fortune – followed.
定位:第 I 节〈Complementary skills〉,p.12,「not to imitate Warren Buffett」
第 5 步没有互补能力的人还有一条路:坐进别人的挎斗。
作者在给出格言之前先放了一道决策题:有人请你加入 Tengion 的商业顾问委员会——这家公司 2003 年成立,要开发并商业化一项医学突破:用病人自身细胞培育新组织与新器官,借助身体的再生能力,让器官衰竭的成人与儿童有可能获得由自体组织构建的功能性器官。加入的一个主要好处是,你可以与公司内部人和风险投资机构以相同条件投入一笔合理的钱。你会投吗?作者说这对他是 UU 情形,而且是双重的——在此之前他从没听过「新生器官」这个词。他投了,理由有三条:他多年前与 Tengion 的总裁在另一家公司成功合作过;他是与有记录、在相关生物科技领域有专长的风投机构以相同条件投资;这是一笔几乎所有其他人都被排除在外的投资;而且它还能借到那些风投的互补能力。这类做法他叫:投资者坐在挎斗里,由一辆强劲的摩托车拉着走。他给出成立条件:投资者越是处在能对车手的诚信与车的性能有把握的独特位置,这笔投资就越有吸引力,因为竞争有限、价格更低。他举的最好例子是几十年前的伯克希尔——你本可以与 Buffett 一同投资,而他为自己的服务只拿极低的报酬(近年是 10 万美元,没有奖金也没有期权);但 1960 年谁听说过 Buffett,谁知道他会是这样一位出色又低薪的投资者?当年认识他并认出他非凡能力的人,就处在一个特权的 UU 位置上。
对照原文
Before presenting a maxim about complementary skills, I present you with a decision problem. You have been asked to join the Business Advisory Board of a company named Tengion. Tengion was founded in 2003 to develop and commercialize a medical breakthrough: “developing new human tissues and organs (neo-tissues and neo-organs) that are derived from a patient’s own cells…[this technology] harnesses the body’s ability to regenerate, and it has the potential to allow adults and children with organ failure to have functioning organs built from their own (autologous) tissues.” http://www.tengion.com/
This is assuredly a UU situation, doubly so for you, since until now you had never heard the term neo-organ. A principal advantage of joining is that you would be able to invest a reasonable sum on the same basis as the firm’s insiders and venture capitalists. Would you choose to do so?
I faced this decision problem because I had worked successfully with Tengion’s president on another company many years earlier. I was delighted with the UU flavor of the situation, and chose to join and invest because I would be doing so on the same terms as sophisticated venture capital (VC) firms with track records and expertise in relevant biotech areas. This was an investment from which virtually everyone else would be excluded. In addition, it would benefit from the complementary skills of the VCs.
Such undertakings are “sidecar investments”; the investor rides along in a sidecar pulled by a powerful motorcycle. The more the investor is distinctively positioned to have confidence in the driver’s integrity and his motorcycle’s capabilities, the more attractive the investment, since its price will be lower due to limited competition. Perhaps the premier sidecar investment ever available to the ordinary investor was Berkshire Hathaway, many decades back. One could have invested alongside Warren Buffett, and had him take a ridiculously low compensation for his services. (In recent years, he has been paid $100,000, with no bonus or options.) But in 1960 who had heard of Warren Buffett, or knew that he would be such a spectacular and poorly compensated investor? Someone who knew Buffett and recognized his remarkable capabilities back then was in a privileged UU situation.
定位:第 I 节〈Sidecar investments〉,p.12–13,「the investor rides along in a sidecar」
第 6 步格言 A:有互补能力的人赚到很高的超额回报,有机会就在他们旁边投。
前面五步是前提,这里是作者编号的第一条格言。 把两件事合成一句:第一,具备互补能力的个人从 UU 投资中享有很高的正超额回报(这是站 04 前四步的结论);第二,因此当有机会时,在他们旁边做一笔挎斗投资。注意它的语法:格言的动作是「在他们旁边投」,不是「学他们那样投」,这正好接住第 4 步那句「不要模仿」。
对照原文
Maxim A: Individuals with complementary skills enjoy great positive excess returns from UU investments. Make a sidecar investment alongside them when given the opportunity.
定位:第 I 节,p.13,「Maxim A」
第 7 步Gazprom 是这条格言的压力测试:做不了传统尽调,能依靠的只有猜想 1 与格言 A。
作者立刻问:你有勇气应用这条格言吗?然后摆出 2006 年 1 月的 Gazprom。正面是:俄罗斯正试图吸引西方机构投资;股票以 形式出售,即将在场外市场挂牌;公司利润极其丰厚,而且它卖气的价格只是世界价格的一小部分;众所周知大量俄罗斯精英是投资者,而且它在一些地方正大幅提价。反面是:Gazprom 被用作俄罗斯政府政策的工具——因为白俄罗斯政府友好,气价被高额补贴;而乌克兰因为政府对莫斯科不友好,面临四倍以上的涨价威胁;公司臃肿、管理糟糕;而 Yukos 石油的经历表明政府强大、反复无常且冷酷。作者说这明显是无知即 UU:未来的状态根本不知道——现政府会继续执政吗?它会把 Gazprom 当成吸引西方投资的旗舰吗?如果会,它会精简运营吗?它把外交顾虑主要当成涨价的工具吗(那是强烈的正面信号),它是否走在全面提价的路上?它会完成通往欧洲的管道吗?还有哪些你根本没想到的问题,它们的答案可能剧烈改变你的收益?他还要求你另外查两件事:西方投资者作为 Gazprom 股东有没有独特的劣势(特殊税负、次级投票权等),以及如果现在看起来有利,俄罗斯多快能把条件改得对外人不利、你是否会警觉并在变化开始时退出。结论是:你永远无法把这些不可知学到足以做传统尽调的程度;支持你下手的主要论据只有猜想 1 与格言 A——如果你能确信俄罗斯精英是出于自己的意愿在投资,且外国人不会(至少不会很快)被歧视,这就是一笔合理的挎斗投资。作者在脚注里交代了这道题的时间与结果:这笔投资是 2006 年 1 月 6 日在沃顿商学院主办的一次会议上提出的,当时价格是 33.60;九个月后本文付印时是 47 美元。他在后面的复盘一节里也只给了这一句结论:三笔决策题里,Gazprom 在六个月里表现不错。
对照原文
Do you have the courage to apply this maxim? It is January 2006 and you, a Western investor, are deciding whether to invest in Gazprom, the predominantly government-owned Russian natural gas giant in January 2006. Russia is attempting to attract institutional investment from the West; the stock is sold as an ADR, and is soon to be listed on the OTC exchange; the company is fiercely profitable, and it is selling gas at a small fraction of the world price. On the upside, it is generally known that large numbers of the Russian elite are investors, and here and there it is raising its price dramatically. On the downside, Gazprom is being employed as an instrument of Russian government policy, e.g., gas is sold at a highly subsidized price to Belarus, because of its sympathetic government, yet the Ukraine is being threatened with more than a four-fold increase in price, in part because its government is hostile to Moscow. And the company is bloated and terribly managed. Finally, experiences, such as those with Yukos Oil, make it clear that the government is powerful, erratic, and ruthless.
This is clearly a situation of ignorance, or UU. The future states of the world are simply not known. Will the current government stay in power? Will it make Gazprom its flagship for garnering Western investment? If so, will it streamline its operations? Is it using foreign policy concerns as a device mainly to raise prices, a strong positive, and is it on a path to raise prices across the board? Will it complete its proposed pipelines to Europe? What questions haven’t you thought of, whose answers could dramatically affect your payout? Of course, you should also determine whether Western investors have distinct disadvantages as Gazprom shareholders, such as unique taxes, secondary voting status, etc. Finally, if you determine the investment is favorable given present circumstances, you should ask how quickly Russia could change conditions against outsiders, and whether you will be alert and get out if change begins.
You could never learn about the unknowables sufficiently well to do traditional due diligence on a Gazprom investment. The principal arguments for going ahead would be that Speculation 1 and Maxim A apply. If you could comfortably determine that the Russian elite was investing on its own volition, and that foreigners would not be discriminated against, or at least not quickly, this would make a sensible sidecar investment.¹⁰
定位:第 I 节,p.13–14,「deciding whether to invest in Gazprom」
四类互补能力,以及你能不能借到
| 持有者 | 能力具体是什么 | 回报从哪里来 | 你能不能借到 |
|---|---|---|---|
| 房地产开发商 | 知道在哪儿建、建什么、怎么建 | 在自己的资本上赚到巨额回报 | 很难自己学;可以与之同条件入场 |
| 风险投资人 | 早期公司需要的技能与人脉 | 自有资金的非凡回报,加上向出资人收的费用 | 挎斗投资的典型对象——作者投 Tengion 就是这一类 |
| 高科技先驱 | 远见与科学洞察(作者举 Bill Gates 为极端例子) | 每一块投资美元拿到更高的倍数 | 几乎借不到;能借到的是他们公司的股权 |
| 不寻常的判断力 | 判断何时投入、何时避开 UUU 局面(Miller、Buffett) | 错误定价严重时的显著优势;有时还能拿到折价 | 作者说不要模仿;能借的是与他们同车 |
读表最快的办法:看最后一列。前三行你要找的是「同条件入场的机会」,第四行作者明确说不要模仿。
这一站的结论
UU 投资的超额回报付给的是与资本互补的稀缺能力,不是资本本身。你要么自己有这种能力,要么与有能力的人同条件入场——后者就是挎斗投资,它成立的前提是你对车手的诚信与车的性能有别人没有的把握。Gazprom 这类做不了传统尽调的机会,能依靠的也只有猜想 1 与格言 A。
想一想:作者投 Tengion,他实际上在投的是什么?如果他只是读了公司网站上那段关于新生组织与新生器官的介绍,他会投吗?
写下你的答案再展开
他投的不是技术判断——他自己说在此之前没听过「新生器官」这个词。他投的是三件别人拿不到的东西:与总裁多年前的合作经历(对人的把握)、与专业风投完全相同的条件(利益一致)、以及一笔几乎所有人都被排除在外的入场权(竞争稀薄)。只读公司介绍的话,这三件一件都没有,那就只剩一个听不懂的技术故事。见本站第 5 步。
边界:这一站哪些话要打折扣
- 「与风投同条件」说的是价格与轮次,不等于同权利。清算优先权、反稀释、跟投权这些条款本文完全没有讨论,而它们决定坏结果下你排在第几位。
- Tengion 与 Gazprom 都是 2006 年的情境,作者写作时结果未定。本课不追踪这两家公司后来的结果,因为作者要检验的是决策过程,不是结果。
- 「大投资者乐于公开成功」是作者的观察,不是对所有市场都成立的一般规律。
下一站:这套做法要求你不被自己的判断骗到——作者接着处理三个行为陷阱。
05 / 三个行为陷阱
过度自信、回忆偏差,与不分辨小概率
第 1 步UU 正是你经验最少、直觉没被磨过的地方,所以行为陷阱在这里最贵。
作者的前提是行为决策这门学问的描述性效力:近几十年它撼动了经济学与金融学,在一个又一个领域显示个体系统性地偏离 Savage(1954)与 Raiffa(1968)那种会被称赞的理性决策方式。他举的一个例子是这些偏离者可以被变成「抽水泵」:他们会付钱选赌局 B 而不是 A;随后把 A 重新表述成 A′(基本面完全没变),他们又会付钱选 A 而不是 B。作者说这显然不是审慎投资之路,但行为决策确实有很强的描述效力。推演落到本文:几乎就定义而言,UU 情形正是我们经验有限的地方,是我们不会遇到那些帮我们磨出直觉的相似情境的地方。结论:处理不可知时,我们几乎所有人都会掉进重要的决策陷阱。这一节他讲两个(过度自信与回忆偏差),再重点讲第三个(错误加权概率与赔付)。
对照原文
Behavioral decision has shaken the fields of economics and finance in recent decades. Basically, this work shows in area after area that individuals systematically deviate from making decisions in a manner that would be admired by Jimmie Savage (1954) and Howard Raiffa (1968), pioneers of the rational decision paradigm. As one illustration, such deviators could be turned into money pumps: They would pay to pick gamble B over gamble A. Then with A reframed as A’, but not changed in its fundamentals, they would pay to pick A over B.
That is hardly the path to prudent investment, but alas behavioral decision has strong descriptive validity. Behavioral decision has important implications for investing in UU situations. When considering our own behavior, we must be extremely careful not to fall prey to the biases and decision traps it chronicles. Almost by definition, UU situations are those where our experience is likely to be limited, where we will not encounter situations similar to other situations that have helped us hone our intuition.
Virtually all of us fall into important decision traps when dealing with the unknowable. This section discusses two, overconfidence and recollection bias, and then gives major attention to a third, misweighting differences in probabilities and payoffs. But there are dozens of decision traps, and some will appear later in this essay. The Nobel Prize winning work of Daniel Kahneman and Amos Tversky (the latter was warmly cited, but died too soon to win),¹¹ and the delightful and insightful Poor Charlie’s Almanack, written by Charles Munger (Warren Buffett’s partner) respectively provide academic and finance-oriented discussions of such traps.
定位:第 II 节,p.14,「Behavioral decision has shaken the fields」
第 2 步对行为经济学的三个常见反对,在 UU 情形里都不成立或正好反过来。
作者先把反方意见摆全,再逐条回应,前提是他要说明这些偏误在本文语境里为什么仍然重要。三个反对是:第一,在竞争市场里这些异象会被套利掉;第二,异象只出现在精心设计的情境里,它们很像视觉错觉,有趣但很少影响日常视觉;第三,它们描述人实际怎么做,而不是人应该怎么做。他的回应逐条对上:第一条与本文的讨论无关,因为许多 UU 情形里根本不存在竞争市场与套利,尤其是我们关心的那些;第二条相对不重要,因为本质上 UU 情形正是「视觉错觉统治世界」的地方,他把 UU 世界比作游乐场的哈哈镜屋;第三条他认真对待,并说这整篇文章正是为了帮人在投资时更理性地行动。
对照原文
There are at least three major objections to behavioral economics: First, in competitive markets, the anomalies it describes will be arbitraged away. Second, the anomalies only appear in carefully crafted situations; they are much like optical illusions, intriguing but rarely affecting everyday vision. Third, they describe the way people do behave, but not the way they should behave. The first
objection is tangential to this discussion; competitive markets and arbitrage are not present in many UU situations, and in particular not the ones that interest us. The second objection is relatively unimportant because, in essence, UU situations are those where optical illusions rule the world. A UU world is not unlike a Fun House. Objection three I take up seriously below; this essay is designed to help people behave more rationally when they invest.
定位:第 II 节,p.14–15,「three major objections to behavioral economics」
第 3 步过度自信:理论上约 2% 落在意外点之外,实际约 35%。
作者的前提来自 Alpert 与 Raiffa 1982 年的研究:当人们评估自己知之甚少的数量时,他们对自己的知识过于自信。他在附录 A 给了读者一套自测:对八个未知数量(比如芬兰的面积),先给中位数估计,再给第 25 与第 75 百分位(也就是真值落在这两个数之外的可能性各占四分之一),最后给第 1 与第 99 百分位——后两者被称作意外点(surprise points)。推演是纯粹的定义:按概率的含义,一个人应当只有约 2% 的时候,真值会落在自己的意外点之外。实际数字是:即使事先被警告过度自信,人们仍有约 35% 的时候被意外。结论用作者自己的话说很简单:人们以为自己对不可知的数量了解得远比实际多。
对照原文
When individuals are assessing quantities about which they know very little, they are much too confident of their knowledge (Alpert and Raiffa, 1982). Appendix A offers you a chance to test your capabilities in this regard. For each of eight unknown quantities, such as the area of Finland, you are asked to provide your median estimate, then your 25th and 75th percentile estimates (i.e., it is one quarter likely the true value will be more extreme than either of the two), and then your 1st and 99th percentiles, what are referred to as surprise points. In theory, an individual should have estimates outside her surprise points about 2% of the time. In fact, even if warned about overconfidence, individuals are surprised about 35% of the time.¹² Quite simply, individuals think they know much more about unknowable quantities than they do.
定位:第 II 节〈Overconfidence〉,p.15,「much too confident of their knowledge」
第 4 步猜想 2:过度自信的人是这个生态里的草。
把上一步的实验结果接到投资上,就是作者编号的:对自己的知识过度自信的人,会在 UU 世界里做出糟糕的投资。他随后给了一个生态比喻,并且把读者放进去:金融这个精致的生态系统里狮子很少,比如 Bill Miller 和 Warren Buffett;羚羊很多,「比如你和我」;还有广袤的草地,最终养活了所有人。这个比喻的作用是给猜想 2 定位:它说的不是「别人」,而是包括读者自己在内的大多数。
对照原文
Speculation 2: Individuals who are overconfident of their knowledge will fall prey to poor investments in the UU world. Indeed, they are the green plants in the elaborate ecosystem of finance where there are few lions, like Bill Miller and Warren Buffett; many gazelles, like you and me; and vast acres of grass ultimately nourishing us all.
定位:第 II 节〈Overconfidence〉,p.15,「Speculation 2」
第 5 步回忆偏差:你以为在复盘判断,其实在复盘被污染的记忆。
作者的前提是一条自然的自我改进建议:处理 UU 情形的第一课是认识你自己,而做到这一点的一个好办法是复盘过去决策的成败。他马上指出这条路上的坑:由于人们没有长期记录,他们自然会转向过去的假设性问题——「我当初会不会判断那件真的发生了的事很可能发生?」「我会不会做那笔好投资、避开那笔坏投资?」「我会不会在 2001 年新年前后清掉纳斯达克的股票?」作者说人类不擅长回答这类问题,他们受到严重的影响。证据是他自己参与的研究:从 9/11 之前《纽约时报》的报道判断,当时几乎没有人预期美国会遭遇一场大规模恐怖袭击,那是一次明确的 UUU 事件。但事发一到三年后,超过 300 名哈佛法学院与肯尼迪学院的学生被问及「把你现在对大规模恐袭可能性的评估,与你估计自己在 2001 年 9 月 1 日时的评估相比」时,31% 认为现在的风险更低,26% 认为与事发前所感知的相同。结论:我们几乎无法相信投资者有能力判断自己当初会怎样评估那些已经发生的 UU 风险。
对照原文
A first lesson in dealing with UU situations is to know thyself. One good way to do this is to review successes and failures in past decisions. However, since people do not have a long track record, they naturally turn to hypotheticals from the past: Would I have judged the event that actually occurred to be likely? Would I have made that good investment and steered clear of the other bad one? Would I have sold out of NASDAQ stocks near New Year 2001? Alas, human beings do not do well with such questions. They are subject to substantial recollection bias.¹³
Judging by articles in the New York Times leading up to 9/11/2001, there was virtually no anticipation of a major terrorist attack on the United States; it
was a clear UUU event. But that is not what respondents told us one to three years later. They were asked to compare their present assessments of the likelihood of a massive terrorist attack with what they estimated that likelihood to be on September 1, 2001. Of more than 300 Harvard Law and Kennedy School students surveyed, 31% rated the risk as now lower, and 26% rated the risk as the same as they had perceived the 9/11 risk before the event.¹⁴ We can hardly be confident that investors will be capable of judging how they would have assessed UU risks that occurred in the past.
定位:第 II 节〈Recollection bias〉,p.15–16,「subject to substantial recollection bias」
第 6 步人不能充分区分两个小概率:许多人选期望值更低的那个。
作者的前提是决策问题的两个要素:赔付与概率,两者都必须被仔细校准。他说毫不意外地,迄今对行为决策理论最重要的单项贡献————发现人们对赔付和概率的反应都远非理性。他自己加了一句限定:据他所知,没有人统计过这两者中哪一个对「相对理性基准的期望效用损失」贡献更大;他还括注了一个不同意见:一些行为决策理论的坚定支持者认为,是我们的规范搞错了,大脑自然感知结果的方式才应该是准绳,而不是决策理论家与经济学家的处方。推演落到一个具体实验:请人在 A 与 B 之间选,A 是 1% 概率拿 $2000,B 是 2.5% 概率拿 $1000。理性且风险厌恶的人应当选 B,因为它期望值更高($25 对 $20)而且风险更小;但过去的实验显示许多人选 A,因为按前景理论,他们不能充分区分两个低概率事件。作者顺手加了一条猜测:如果把概率换成具名的偶发事件(比如太空人队或蓝鸟队赢得世界大赛),并配上相同的概率,选 A 的频率还会更高。这条猜测是接下来一步的引信:A/B 是基线(两边都是数字概率),C/D 换掉一边(一边是数字、一边是具名的 UU 事件),E/F 把两边都换成 UU 事件——三组一层比一层远离数字,作者预期偏离也一层比一层大。本站步骤之后的那张对照表把三组并排放着,读第 7 步时可以对照着看。
对照原文
The two critical components of decision problems are payoffs and probabilities. Effective decision requires that both be carefully calibrated. Not surprisingly, Prospect Theory, the most important single contribution to behavioral decision theory to date, finds that individuals’ responses to payoffs and probabilities are far from rational.¹⁵ To my knowledge, there is no tally of which contributes more to the loss of expected utility from the rational norm. (Some strong supporters of behavioral decision theory, however, think it is our norms that are misguided, and that the way the brain naturally perceives outcomes, not the prescriptions of decision theorists and economists, should be the guideline.)
Whether drawing from Prospect Theory or observation, it seems clear that individuals draw insufficient distinctions among small probabilities. Consider the following experiment, in which an individual is asked to pick A or B.
Lottery Choice: Payoffs Versus Probabilities
| | Payoff | Probability | |---|---|---| | A | $2000 | 0.01 | | B | $1000 | 0.025 |
A rational, risk averse individual should opt for B, since it offers a higher expected value – $25 versus $20 – and less risk. Yet past experiments have shown that many individuals choose A, since in accordance with Prospect Theory they do not distinguish sufficiently between two low probability events. We speculate further that if we used named contingencies – for example, the Astros or the Blue Jays win the World Series – alongside their probabilities, the frequency of preference for A would increase. The contingencies would be selected, of course, so that their likelihood of occurrence, as indicated by odds in Las Vegas, would match those in the example above.
定位:第 II 节〈Misweighting probabilities and preferences〉,p.16,「Lottery Choice: Payoffs Versus Probabilities」
第 7 步把概率换成具名的 UU 事件,偏离更大;模糊厌恶因此加强了猜想 1。
作者用 A/B 作基线,接着换成 C/D:C 是从编号 1 到 100 的罐子里摸到 17(1%),D 是「一颗一万吨重的小行星曾在四万英里内掠过地球」——这个距离是先请一批人猜、再反复调整参数直到中位数答案落在 0.03 得到的。他猜想:选 C 而不选 D 的人,会比之前选 A 而不选 B 的人更多。再进一步,E/F 把两边都换成 UU 事件:E 是「校准过的大量动物越过坦桑尼亚—肯尼亚边境」(1%),F 仍是那颗小行星(3%)。他推测 E 仍会被频繁选中。结论是那句核心判断:人们不喜欢让自己的收益依赖 UU 事件是否发生,而基于这些事件的概率去做区分,对他们来说是一个不自然的动作。作者随后把这条接到 Ellsberg 1961 年的上:人宁可靠一枚标准硬币的正面来赢奖,也不愿在一枚结果难以预测的变形硬币上选正或反。他给出一个可能的解释,并且立刻说明这个解释本身是合理的:在一般的不确定决策里,对面常常有一个更知情的人——比如正在卖给你一件难以评估的资产的人——所以模糊厌恶可能是一个合理的启发式回应。但他把它再推一步:越模糊的偶发事件,厌恶越强;如果是这样,UU 投资会赶走除了最自主、最理性的思考者之外的所有投资者。于是猜想 1 得到加强——别人的模糊厌恶,正是你那个低价的来源。
对照原文
This hypothetical experiment establishes a baseline for another one that involves UU events. This time the prizes are based on events that are as close to the spectrum of UU events as possible, subject to the limitation that they must be named.¹⁶ Thus, a contingency might be that a 10,000-ton asteroid passed within 50,000 miles of Earth within the past decade, or that more than a million mammals crossed the border from Tanzania to Kenya last year. To begin our experiment, we ask a random sample of people to guess the likelihood of these contingencies. We then alter the asteroid distance or the number of animals in the question until the median answer is 0.03. Thus, if 50,000 miles got a median answer of 0.05, we would adjust to 40,000 miles, etc.
We now ask a new group of individuals to choose between C and D, assuming that we have calibrated the asteroid and mammal question to get to 0.03.
Lottery Choice: Payoffs Versus Probability or UU Event
| | Payoff | Required contingency | |---|---|---| | C | $2000 | Draw a 17 from an urn with balls numbered 1 to 100 | | D | $1000 | 10,000-ton asteroid passed within 40,000 miles of Earth |
Lotteries C and D should yield their prizes with estimated probabilities of 1% and 3% respectively. Still, we suspect that many more people would pick C over D than picked A over B, and that this would be true for the animal movement contingency as well.¹⁷
定位:第 II 节,p.17,「Lottery Choice: Payoffs Versus Probability or UU Event」
对照原文
Lottery Choice: Payoffs Versus UU Events
| | Payoff | Required contingency | |---|---|---| | E | $2000 | Calibrated large number of animals crossed the Tanzania-Kenya border | | F | $1000 | 10,000 ton-asteroid passed within 40,000 miles of Earth |
Here the values have been scaled so the median response is three times higher for the asteroid event than the animal crossing. We would conjecture again that E would be chosen frequently.¹⁸ People do not like to rely on the occurrence of UU events, and choices based on distinguishing among their probabilities would be an unnatural act.
Daniel Ellsberg (1961) alerted us to ambiguity aversion long before he created a UU event by publishing the Pentagon papers. In an actual experiment, he showed, in effect, that individuals preferred to win a prize if a standard coin flip came up heads, rather than to win that prize by choosing either heads or tails on the flip of a mangled coin whose outcome was difficult to predict.¹⁹ Such ambiguity aversion may be a plausible heuristic response to general decisions under uncertainty, since so often there is a better-informed person on the other side – such as someone selling a difficult-to-assess asset.²⁰ Whatever the explanation, ambiguity aversion has the potential to exert a powerful effect. Extending Ellsberg one step further, it would seem that the more ambiguous the contingencies, the greater the aversion. If so, UU investments will drive away all but the most self-directed and rational thinking investors. Thus, Speculation 1 is reinforced.
定位:第 II 节,p.18,「People do not like to rely on the occurrence of UU events」
先猜再看:下面这两个抽奖,你选哪一个?先记下你的选择,再往下读作者的期望值。
三组抽奖的对照
| 组别 | 高赔付的一边 | 低赔付的一边 | 理性选择 | 作者预期的实际选择 |
|---|---|---|---|---|
| A / B(都是数字概率) | A:$2000,概率 0.01(期望 $20) | B:$1000,概率 0.025(期望 $25) | B(期望更高且风险更小) | 许多人选 A |
| C / D(一边是 UU 事件) | C:$2000,从 1–100 的罐子里摸到 17(1%) | D:$1000,一万吨小行星在四万英里内掠过地球(校准到 3%) | D(期望 $30 对 $20) | 选 C 的比例比选 A 的更高 |
| E / F(两边都是 UU 事件) | E:$2000,校准过的大量动物越过坦桑尼亚—肯尼亚边境(1%) | F:$1000,同一颗小行星(3%) | F(期望 $30 对 $20) | E 仍会被频繁选中 |
读表最快的办法:从左往右看「理性选择」这一列——三组的正确答案都是低赔付那一边,而作者预期人们三次都倒向高赔付那一边,且越往下越严重。
这一站的结论
过度自信让你以为自己对不可知的数量了解得比实际多;回忆偏差让复盘失去校准作用;对小概率的不分辨会让你在 UU 世界里付错价。而同一组偏误作用在别人身上时方向相反:他们的模糊厌恶把他们赶出这个市场,于是价格对留下来的人有利。
边界:这一站的数字来自哪里
- 「约 35% 被意外」是作者自己高管课程与政策分析课 2001–2006 年的近似平均,不是公开数据集,本课未做外部核对。
- C/D 与 E/F 两组是作者设计但未实施的实验,他用的词是 suspect 与 conjecture;页面上呈现的是他预期的方向,不是观测到的比例。
- 9/11 那项调查的样本是哈佛法学院与肯尼迪学院的学生,不是一般投资者。
下一站:如果对手是数学高手,机会还在不在;以及有优势的时候该投多少。
06 / 数学高手与下注比例
不要在数学高手的场子里投;有优势时该投多少
第 1 步传统市场的对手越来越聪明;超额回报在数学博士进场的领域里消失。
作者的前提是一个关于人力的观察:受过教育的专业人士大量涌入金融。由此推演:那些靠在传统市场上投机与交易为生的人,越来越多地面对极其聪明、掌握极其充分信息的对手。他在脚注里请出 Paul Samuelson 作旁证:Samuelson 说,由前石溪数学教授 Jim Simons 掌管的文艺复兴集团,「也许是传统金融市场里唯一一个长期的、经风险调整后的惊人表现者」。结论被作者写成一句新谚语,对照的是旧谚语「如果擦鞋童都给你股票建议,就该离场了」:如今擦鞋童几乎消失,金融博士遍地——当你的数学高手朋友告诉你,他和同行被雇去做 XYZ 领域时,XYZ 领域的惊人回报很可能已经永远消失了。
对照原文
The major fortunes in finance, I would speculate, have been made by people who are effective in dealing with the unknown and unknowable. This will probably be truer still in the future. Given the influx of educated professionals into finance, those who make their living speculating and trading in traditional markets are increasingly up against others who are tremendously bright and tremendously well-informed.²¹
By contrast, those who undertake prudent speculations in the unknown will be amply rewarded. Such speculations may include ventures into uncharted areas, where the finance professionals have yet to run their regressions, or may take completely new paths into already well-traveled regions.²² It used to be said that if your shoeshine boy gave you stock tips it was time to get out of the market. With shoeshine boys virtually gone and finance Ph.D.’s plentiful, the new wisdom might be:
When your math whiz finance Ph.D. tells you that he and his peers have been hired to work in the XYZ field, the spectacular returns in XYZ field have probably vanished forever.
定位:第 III 节,p.19,「the influx of educated professionals into finance」
第 2 步反过来说:越难调查的领域 UU 越多,妥善处理者的期望利润越高。
这一步是上一步的镜像。前提相同——竞争会消耗超额回报;推演相反——那么在竞争难以进入的地方,超额回报应当留存。作者说,一个领域越难调查,与之相关的未知与不可知就越多,妥善处理它们的人的期望利润也就越高。他随即加了一条重要的自我限定:不可知不能被转化成明智的猜测——这一点他不打算含糊;但人可以安排自己的仓位、排布自己的权利,让未知与不可知多半成为盟友而非敌人。而且人可以训练自己避开自身的行为决策倾向,并利用别人的那些倾向。结论:站 05 的内容在这里变成了两件可做的事,一件是防守(练自己),一件是进攻(用别人的)。
对照原文
Similarly, the more difficult a field is to investigate, the greater will be the unknown and unknowables associated with it, and the greater the expected profits to those who deal sensibly with them. Unknownables can’t be transmuted into sensible guesses -- but one can take one’s positions and array one’s claims so that unknowns and unknowables are mostly allies, not nemeses. And one can train to avoid one’s own behavioral decision tendencies, and to capitalize on those of others.
定位:第 III 节,p.19,「the more difficult a field is to investigate」
第 3 步有优势时该投多少?Kelly 给出 W − (1−W)/R。
作者把问题具体化:假设一个投资者愿意在自己有优势的 UU 情形里下手,那么每个机会该投入多少资本?他先说明这不是通常的组合问题——它被无知困扰,而且决策必须以顺序方式做出。他说数学高手们在一支经济学家不太熟悉、但赌徒与数学家常谈的文献里讨论过这个问题,其中最著名的是 50 年前 AT&T 科学家 J. L. Kelly 的一篇文章,其基本公式与 Claude Shannon 的信息论密切相关:它告诉你每一次赌局该以本金的多少下注,参数只有两个——获胜概率和赔率。作者提示了一个也许令人意外的性质:未来投资机会的构成并不影响结果。的写法是:投入等于 W − (1−W)/R 的金额,W 是你获胜的概率,R 是你赢时所得与输时所失之比。作者给出的例子:如果你有 60% 的概率赢一个等额赌局,你就投 .6 − (1−.6)/1 = .2,即两成本金。他补充了这条准则的数学地位:可以证明,给定足够长的时间,任何其他投资策略的价值最终都会被遵循 Kelly 准则的价值超过,因为它最大化组合的几何增长率。
对照原文
Assume that an investor is willing to invest where he has an edge in UU situations. How much capital should then be placed into each opportunity? This
problem is far from the usual portfolio problem. It is afflicted with ignorance, and decisions must be made in sequential fashion. Math whizzes have discussed this problem in a literature little known to economists, but frequently discussed among gamblers and mathematicians. The most famous contribution is an article published 50 years ago by J.L. Kelly, an AT&T scientist. His basic formula, which is closely related to Claude Shannon’s information theory, tells you how much to bet on each gamble as a function of your bankroll, with the probability of winning and the odds as the two parameters. Perhaps surprisingly, the array of future investment opportunities does not matter.
Kelly’s Criterion, as it is called, is to invest an amount equal to W – (1-W)/R, where W is your probability of winning, and R is the ratio of the amount you win when you win to the amount you lose when you lose. Thus, if you were 60% likely to win an even money bet, you would invest .6 – (1-.6)/1 = .2 or 20% of your capital.
It can be shown that given sufficient time, the value given by any other investment strategy will eventually be overtaken in value by following the Kelly Criterion, which maximizes the geometric growth rate of the portfolio. That might seem to be definitive. But even in the mathematical realm of optimal dynamic investment strategies, assuming that all odds and probabilities are known, we encounter a UU situation.
定位:第 III 节,p.19–20,「Kelly’s Criterion, as it is called」
第 4 步Samuelson 的反驳:最优投入取决于效用函数,Kelly 只对对数效用恰好正确。
作者说「那看起来像是定论了」,然后自己把它推翻一半。前提是:即使在「所有赔率与概率都已知」的最优动态投资策略这个数学领域里,我们也会遇到一个 UU 情形。Paul Samuelson 用一种玩闹的笔调写了一篇攻击 Kelly 准则作为实践指南的文章,全篇只用单音节词,摘要是:「他,在 N 次下注中把自己财富的对数均值做到最大的人,将以随 N 增大而趋近于 1 的胜算,赢过按我自己的风险口味行事的我。」推演:Samuelson 正确地指出,在赔率有利的情形下——无论是否重复——一个最大化期望效用的人应当投入的最优金额,取决于他的效用函数。作者给了一个极端例子帮助直觉:一个风险中性的投资者,每当遇到赔率有利的局面就应当投入全部财富,而不是 Kelly 提出的那个「神奇比例」;用扑克的话说就是 all in——这会在任何有限期数里最大化他的期望总财富,因而最大化他的期望效用。结论:Kelly 准则虽然在数学上正确,却不应指导投资者的行动,因为它忽略了偏好结构。作者补上定量的对应关系:把偏好算进来之后,Kelly 准则恰好给出正确的投资比例——如果你的效用函数是;对风险厌恶程度更低的效用函数它过于保守,反之亦然。他给出对数效用的一个可检验特征:这样的人恰好会接受一个等额赌局,把财富乘以 1+x 或除以 1+x,对任何 x 都成立——比如把财富翻倍或减半的等额赌局。
对照原文
Paul Samuelson, writing in a playful mood, produced an article attacking the Kelly Criterion as a guide for practice. His article uses solely one-syllable words. His abstract observes: “He who acts in N plays to make his mean log of wealth as big as it can be made will, with odds that go to one as N soars, beat me who acts to meet my own tastes for risk.”²³ Samuelson correctly prescribes that in favorable-odds situations, whether repeated or not, the optimal amount for an individual who maximizes his expected utility to invest will depend on his utility function. To promote your intuition, consider a polar case. A risk-neutral investor should invest his total wealth whenever he confronts a favorable-odds situation, as opposed to the “magic fraction” proposed by Kelly. Going all in, to use poker terminology, will maximize his expected total wealth, hence his expected utility, for any finite number of periods.²⁴ In short, Samuelson shows that the Kelly Criterion, though mathematically correct, should not guide an
investor’s actions, since it ignores the structure of preferences, whether risk neutral or risk averse.²⁵
Accounting for preferences, it turns out that the Kelly Criterion leads to precisely the right investment proportions if one’s utility function is logarithmic, but it is too conservative for less risk-averse utility functions, and vice versa. With logarithmic utility, one will just take an even money bet that either multiplies one’s wealth by 1+x or by 1/(1+x), for any x. Thus, one would take an even money bet to double or halve one’s wealth.
定位:第 III 节,p.20–21,「Samuelson, writing in a playful mood」
第 5 步即使 Kelly 正确,它的设定也抓不住 UU 的现实:五点困难。
作者先说明自己的限度:他没有篇幅也没有能力把顺序投资问题理清楚。但他列出五点,说明即便 Kelly 准则是对的,它所采用的表述也无法涵盖多数真实世界的投资机会:(1) 多数 UU 投资在相当长的一段时间里不流动,而且这段时间往往长度未知——今天投出去的钱在变现之前无法再投资;(2) 市场为变现非流动资产索取巨额溢价——他在脚注里给了一个数字:房地产里几年后到期的有限合伙权益,售价通常比折现的预期未来价值低约 30%,而这个折价反映的正是收购方的互补能力(他们必须有能力评估并释放这些特异合伙权益的价值);(3) 最优顺序投资策略的模型往往把最重要的现实挑战假设掉了,比如不确定的锁定期;(4) 即便是「玩具问题」(那种已知概率、即刻结算的投资),文献里也有实质分歧;(5) 总的结论是:在 UU 问题里资金管理是一项艰难的任务,它甚至困扰那些在这类投资上确有显著优势的人。作者补了一个具体场景:当不可知真的发生时——比如 1987 年股市的那次空中陷落,或者 1997 年的亚洲危机——未曾预料的短期资金管理问题会冒出来,例如为了赶上追加保证金而在市场之间调拨资金。这五点合起来的意思是:就算我们弄清了「一连串即时结算的有利赌局该怎么投」,对真实的 UU 投资世界也帮助甚微。
对照原文
I lack both the space and capability to straighten out the sequential investment problem. But I should make a few observations to point out that even if the Kelly Criterion were correct, the formulation it employs does not capture most real world investment opportunities: (1) Most UU investments are illiquid for a significant period, often of unknown length. Monies invested today will not be available for reinvestment until they become liquid. (2) Markets charge enormous premiums to cash out illiquid assets.²⁶ (3) Models of optimal sequential investment strategies tend to assume away the most important real-world challenges to such strategies, such as uncertain lock-in periods. (4) There are substantial disagreements in the literature even about “toy problems,” such as those with immediate resolution of known-probability investments. The overall conclusion is that: (5) Money management is a challenging task in UU problems. It afflicts even those with a substantial edge when making such investments. And when the unknowable happens, as it did with the air-pocket plunge in the 1987 stock market or the 1997 Asian crisis, unforeseen short-term money-management problems – e.g., transferring monies across markets in time to beat margin calls – tend to emerge. These five points imply that even if it were clear how one should invest in a string of favorable gambles each of which is resolved instantaneously, that would help us little in the real world of UU investing, which presents a much more difficult task.
定位:第 III 节,p.21,「I lack both the space and capability」
第 6 步格言 B:优势越大,投入本金的比例应当越大。
作者说,虽然他对 Kelly 准则挑了不少毛病,它还是提出了一个简单而中心的观点,而这个观点几乎被所有投资建议漏掉了。前提是:多数建议聚焦于有效或接近有效的市场,这意味着你在任何投资上都不会有多大优势。但现实世界里存在一些普通的投资、一些有吸引力的投资、以及一些非常有吸引力的投资;显然,在更有吸引力的投资上投得更多是合理的。这就得到:你在一笔投资上的期望回报越高——也就是你的优势越大——你应当投入风险的本金比例就越大。作者随即指出执行上的落差:多数投资者一经点明就能凭直觉理解这条标准,但他们几乎不执行,或者执行得远远不够——他们预期 30% 回报的那笔投资,拿到的钱只比预期 10% 的那笔多一点点。他的结论句是:在决定如何分配组合时,投资优势应当与分散化的顾虑同等重要。
对照原文
Though I have quibbled about the Kelly Criterion, it makes a simple, central point that is missed in virtually all investment advice. Most such advice
focuses on efficient or near efficient markets, implying that one will not have a great edge in any investment. In contrast, the real world presents some ordinary investments, some attractive investments, and some very attractive investments. Clearly it makes sense to invest more in the more attractive investments. This leads to a maxim on investment advantage:
Maxim B: The greater is your expected return on an investment, that is the larger is your advantage, the greater the percentage of your capital you should put at risk.
Most investors understand this criterion intuitively, at least once it is pointed out. But they follow it insufficiently if at all. The investment on which they expect a 30% return gets little more funding than the one where they expect to earn 10%. Investment advantage should be as important as diversification concerns in determining how one distributes one’s portfolio.
定位:第 III 节,p.21–22,「Maxim B」
试一试:拖动 W 与 R,看 Kelly 的比例在哪里变成负数
这里配可拖模型,是因为作者只给了一个点(W=0.6、R=1 → 0.2),而这条直线有一个零点,格言 B 的措辞里不含它。拖动之前先回答:在等额赌局里,获胜概率低到什么程度时,公式会说「别下注」?
Kelly 给出的本金比例
读图:横轴是获胜概率 W(0 到 100%),纵轴是公式给出的本金比例(可为负,负数的意思是不下注)。虚线是零线;曲线与零线的交点在 W = 1/(1+R)。这是教学演算,不是仓位建议。
这一站的结论
聪明且信息充分的人已经进场的领域,超额回报多半已经消失;难以调查的领域反过来。至于该投多少,Kelly 在数学上正确却不该指导行动,因为它忽略偏好;而且它的设定抓不住 UU 投资的流动性、锁定期与资金调拨。但它的中心点是对的:投资优势应当和分散化同等重要地决定你投多少。
边界:滑块能说明什么,不能说明什么
- Kelly 的设定假设赔率与概率已知、赌局即时结算、资金可无限分割。作者自己列的五点困难说明这三条在 UU 投资里都不成立,所以页面上的比例是演算,不是仓位建议。
- 模型里的 W 与 R 是你输入的信念,不是观测值。把滑块拖到某个位置,不等于你观察到了那个概率。
- 「Kelly 长期胜过其他策略」的证明要求无限多次独立重复;单笔 UU 投资不满足这个条件。
下一站:把桌子对面那个人的决策算进来——这是全篇最硬的一步。
07 / 对方为什么愿意卖给你
对方为什么愿意卖给你:逆向选择
第 1 步设定:资产对你多值 50%,她知道真实价值,价值在 [0,100] 上均匀分布,你出一次价。
作者先把场景铺清楚。前提有四条:第一,你 100% 确定这件资产对你比对持有它的人更值钱,而且正好高 50%;第二,她知道这件东西对她的真实价值;第三,这个价值在 [0,100] 上均匀分布,也就是说它等可能是 0、1、2、……、100;第四,在 Bazerman 与 Samuelson 1983 年的这个著名博弈里(作者此后简称 BS),你只出一次价,如果她拿到的钱多于她自己的价值,她就接受。推演还没开始,问题先摆在那里:你该出多少?本课注读这个设定时最好先确认一件事:这里没有任何欺骗——她不撒谎,规则也公开——唯一的不对称是「她知道那个数,你只知道分布」。
对照原文
Let us posit that you are 100% sure that an asset is worth more to you than to the person who holds it, indeed 50% more. But assume that she knows the true value to her, and that it is uniformly distributed on [0,100], that is, her value is equally likely to be 0, 1, 2, … 100. In a famous game due to Bazerman and Samuelson (1983), hereafter BS, you are to make a single bid. She will accept if she gets more than her own value. What should you bid?
定位:第 IV 节〈Bazerman-Samuelson example and lessons〉,p.22,「you are 100% sure that an asset」
第 2 步课堂上的典型出价是 50 或 60,推理是「平均 50,对我值 75」。
作者先给出人们实际怎么答,因为下一步的纠正需要一个被纠正的对象。他说,在课堂上提问时,典型的出价是 50 或 60,很少有人低到 20。学生的推理链条是:这件东西对她平均值 50,因此对我值 75;所以出个 50 到 60,赚一笔干净利落的差价。这一步的结论只是描述:这条推理听起来完全合理,而且它用到的两个数(均值 50、倍数 1.5)都没有算错。错的地方在别处——下一步把它指出来。
对照原文(本步用到的句子)
When asked in the classroom, typical bids will be 50 or 60, and few will bid as low as 20. Students reason that the item will be worth 50 on average to her, hence 75 to them. They bid to get a tidy profit.
定位:第 IV 节〈Bazerman-Samuelson〉,p.22,「typical bids will be 50 or 60」
查看本段完整版(第 3 步)第 3 步错在哪里:她只在有利时才卖。出 60,成交时她的平均价值只有 30。
作者点出那条推理的缺陷:卖方只有在自己能赚到的时候才会接受。推演他写得很直:让你来当买方。如果你出 60,当她的价值超过 60 时她不会卖;这意味着,在成交这个条件下,她的平均价值是 30——也就是 0 到 60 之间那个平均数。你的期望价值是这个数的 1.5 倍,即 45。于是当你的出价被接受时,你平均亏 15,也就是 60 减 45。作者接着给出一般结论:容易证明,任何正的出价在期望上都是亏的。他的落点是一句关于人的判断:这个故事的寓意是,人们——即使是决策分析与金融课堂上的人们,这些实验在那里做过许多次——非常不擅长把桌子对面那些人的决策考虑进去。本课注这个机制就是(作者本人在第 IV 节的脚注里用的是这个词,说医疗保险里的同一现象也叫它):不需要对方骗你,只需要对方按自己的利益做选择,你成交到的样本就系统性地变差。
成交时你的净收益 = 1.5 × (出价 ÷ 2) − 出价 = 出价 × (1.5/2 − 1) = −0.25 × 出价
当前替代值(出价 60):0.6 × 60% 概率成交,成交时 1.5 × 30 − 60 = −15
对照原文
When asked in the classroom, typical bids will be 50 or 60, and few will bid as low as 20. Students reason that the item will be worth 50 on average to her, hence 75 to them. They bid to get a tidy profit. The flaw in the reasoning is that the seller will only accept if she will make a profit. Let’s make you the bidder. If you offer 60, she will not sell if her value exceeds 60. This implies that her average value conditional on selling will be 30, which is the value of the average number from 0 to 60. Your expected value will be 1.5 times this amount, or 45. You will lose 15 on average, namely 60-45, when your bid is accepted. It is easy to show that any positive bid loses money in expectation. The moral of this story is that people, even people in decision analysis and finance classrooms, where these experiments have been run many times, are very poor at taking account of the decisions of people on the other side of the table.
定位:第 IV 节〈Bazerman-Samuelson〉,p.22–23,「the seller will only accept if she will make a profit」
第 4 步别把这个例子推得太远:「对方确知时永远不该交易」是错的。
作者在这里主动挡住一个错误的外推。前提是:这个例子一旦被解释清楚,人们有强烈的倾向从中得出错误的推论。他说,许多人的结论是「当对方知道真实价值、而你只知道分布时,你永远不该交易」。他的回应分两层:第一,BS 给的是一个极端例子,几乎相当于一个视觉错觉——被设计出来让直觉失灵的那种;第二,你可能会因此推出「当你的信息非常弥散而对方确知时,即使你有强烈的绝对优势也不该交易」。这一步的结论只有一句:那个结论是错的。证明放在下一步。
对照原文
There is also a strong tendency to draw the wrong inference from this example, once its details are explained. Many people conclude that you should never deal with someone else who knows the true value, when you know only the distribution. In fact, BS offer an extreme example, almost the equivalent of an optical illusion. You might conclude that when your information is very diffuse and the other side knows for sure, you should not trade even if you have a strong absolute advantage.
定位:第 IV 节〈Bazerman-Samuelson〉,p.23,「a strong tendency to draw the wrong inference」
第 5 步反例:区间 [1,2]、出价 2,必成交,期望价值 2.25。差别在于信息落差的大小。
作者用一个可复算的反例推翻那个外推。前提与 BS 完全相同(你多值 50%、她确知、你只知分布),只把分布换成 [1,2] 上的均匀分布,出价 2。推演:出价 2 时你必定买到这件东西(她的价值最多是 2),它的期望价值是 1.5 乘以 1.5,等于 2.25——比你付的 2 多。作者解释差别在哪里:这个例子与先验在 [0,1] 上的那个例子的区别在于,这里的有效信息落差要小得多。他给了一个帮助看清的极端:想想 [100,101] 上的均匀分布——那里几乎没有任何落差。他还加了一条自我限定,括在原文里:在 [1,2] 这个例子里出价 2 确实是最优出价,但「极端出价是最优的」这一点同样不应被推广。结论:真正的变量不是「对方是否确知」,而是「有效信息落差有多大」。
对照原文
That conclusion is wrong. For example, if the seller’s true value is uniform on [1,2] and you offer 2, you will buy the object for sure, and its expected value will be 1.5 times 1.5 = 2.25. The difference between this example and the one with the prior on [0,1] is that here the effective information discrepancy is much smaller. To see this, think of a uniform distribution from [100,101]; there is virtually no discrepancy. (In fact, bidding 2 is the optimal bid for the [1,2] example, but that the extreme bid is optimal also should not be generalized.)
定位:第 IV 节〈Bazerman-Samuelson〉,p.23,「That conclusion is wrong」
试一试:拖动优势倍数,看那条曲线什么时候整体越过零线
这里配可拖模型,是因为作者只算了「出价 60 亏 15」这一个点,而真正的结构是:整条曲线的符号只由优势倍数决定,与出价无关。拖动之前先回答:把出价从 60 降到 20,亏损会不会变成盈利?
乘上成交概率后的期望收益
读图:横轴是你的出价(与她的价值同单位),纵轴是乘上成交概率之后的期望收益。虚线是零线。区间下界固定为 0,因为原文的例子就是 [0,100]。这是教学演算,不代表任何真实资产。
这一站的结论
人非常不擅长把桌子对面那个人的决策算进去:对方愿意成交这件事本身就是信息,算进去之后,很多看着划算的出价其实是亏的。但正确的教训不是「永远别交易」——真正的变量是有效信息落差有多大,落差小的时候,即使对方确知,交易仍然可以是好的。
边界:这个模型省掉了什么
- 模型假设只出一次价、没有沟通、没有后续谈判。作者在站 09 自己说,真实交易通常有多轮来回。
- 均匀分布是为了能手算。换成别的分布,条件期望的形状会变,但「成交条件下的均值低于无条件均值」这件事不变。
- a = 2 这个临界点只在区间从 0 起算时成立。把下界抬高(比如 [1,2]),临界点就不在 2 了——这正是作者反例的要点。
下一站:把「绝对优势」和「信息不对称」分开,再用两张格子判断你在哪一格。
08 / 绝对优势与两张格子
绝对优势、相对知识与两张格子
第 1 步不信任对方是有用的本能,但会被外推到不适用的地方——连队友的信息也不信。
作者把站 07 的教训升级成一般命题:人天生非常不擅长从「市场另一边有一个愿意卖的人」这件事里做推断。他先说明这个本能为什么存在:我们的直觉与早期训练让我们不信任对方,因为他的利益常常与我们相悖;如果有人想说服你他那辆二手车多么神奇,怀疑他、并且更看重你自己的信息,是有帮助的。然而 Tversky 与 Kahneman 1974 年在研究人们使用的启发式时发现,人们倾向于把在某些情形下合理的启发式,外推到不合理的情形上。作者的例子是一个受控实验:两个位置对称、利益完全一致的伙伴,对某个由两参数分布刻画的值持有相同的先验,各自拿到一些关于这个值的信息,而且他们对彼此将收到什么信息也持有相同的先验。他们的目标是做一个收益取决于真值的决定。流程是:两人先各自提交自己的最佳估计(也就是各自的均值),看到对方的均值之后,同时提交新的最佳估计。理论上应该发生两件事:其一,两人在第一次与第二次提交之间,有一半的时间会互相越过;其二,第三次提交时两人应当给出完全相同的估计。实际上,除非参与者是 Robert Aumann 的学生(他 1976 年那篇《同意不同意》正是这个例子的灵感来源),他们很少互相越过,而且第三次提交也远远谈不上收敛。
对照原文
The general lesson is that people are naturally very poor at drawing inferences from the fact that there is a willing seller on the other side of the market. Our instincts and early training lead us not to trust the other guy, because his interests so frequently diverge from ours. If someone is trying to convince you that his second hand car is wondrous, skepticism and valuing your own information highly helps. However, in their study of the heuristics that individuals employ to help them make decisions, Tversky and Kahneman (1974) discovered that individuals tend to extrapolate heuristics from situations where they make sense to those where they do not.
For example, we tend to distrust the other guy’s information even when he is on our side. This tendency has serious drawbacks if you consider sidecar investing – free riding on the superior capability of others – as we do below. Consider two symmetrically-situated partners with identical interests who start with an identical prior distribution about some value which is described by a two-parameter distribution. They each get some information on the value. They also have identical prior distributions on the information that each will receive. Thus, after his draw, each has a posterior mean and variance. Their goal is to take a decision whose payoff will depend on the true value. The individuals begin by submitting their best estimate, namely their means. After observing each other’s means, they then simultaneously submit their new best estimate. Obviously, if one had a tight (loose) posterior his estimate would shift more (less) toward that of his partner. In theory, two things should happen: (a) The two partners should jump over each other between the first and second submission half of the time. (b) The two partners should give precisely the same estimate for the third submission.
In practice, unless the players are students of Robert Aumann²⁷ – his article “Agreeing to Disagree” (1976) inspired this example – rarely will they jump over each other. Moreover, on the third submission, they will not come close to convergence.
定位:第 IV 节〈Drawing inferences from others〉,p.23–24,「very poor at drawing inferences」
第 2 步只要对方能开价或能拒绝,他就在用你没有的信息。
作者把上一步的实验结论写成两句教训。第一句是关于我们自己的:我们深深地倾向于相信自己的信息胜过相信对手的信息,而且没有受过良好训练去分辨什么时候这样做是明智的、什么时候这会让我们变成冤大头。第二句是关于对方的:应当留意信息落差,而它们很少通过马戏团叫卖式的行为暴露出来。他举的例子恰恰是最不起眼的两种:当一个卖方只是给你开一个价,或者(像 BS 那样)他可以在你出价后选择接受或拒绝时,他就已经在使用你所没有的信息了。结论是一句行动指令:你最好保持警觉,并给「这条信息可能值多少」以充分的权重——比如,如果他接受了你的出价,这件东西平均值多少。
对照原文
The moral of this story is that we are deeply inclined to trust our own information more than that of a counterpart, and are not well trained to know when this makes good sense, and when it inclines us to be a sucker. One should also be on the lookout for information disparities. Rarely are they revealed through carnival-barker behavior. For example, when a seller merely offers you an object at a price, or gets to accept or reject when you make a bid (as with BS), he will utilize information that you do not possess. You had better be alert and give full weight to its likely value, e.g., how much the object is worth on average were he to accept your bid.
定位:第 IV 节〈Drawing inferences from others〉,p.24,「The moral of this story」
第 3 步可是按最坏情况取最优,会把你推向「永不投资」。
作者在这里处理一个看似顺理成章、其实致命的反应。前提是:在金融世界里,你总是在「对方可能掌握更多信息」的局面里博弈,必须保持警惕。推演:但除非你有一个严格占优的行动——也就是不管对方的信息是什么它都更好——否则一个 maximin 策略(按最坏情况取最优)几乎总会把你推向「永不投资」,毕竟他的信息完全可能正好让你巨亏。结论:把「对方可能更知情」当成决定性理由,等于把自己排除在所有 UU 机会之外;这条路走不通,所以作者必须给出别的东西——下一步就是。
对照原文
In the financial world one is always playing in situations where the other fellow may have more information and you must be on your guard. But unless you have a strictly dominant action – i.e., it is superior no matter what the other guy’s information -- a maximin strategy will almost always push you never to invest. After all, his information could be just such to lead you to lose large amounts of money.
定位:第 IV 节〈Drawing inferences from others〉,p.24,「a maximin strategy will almost always」
第 4 步两线光明救了这个局面:他很少真能害到你,而且他多半也没打好。
前提是上一步的死路。作者随后放进两线光明。第一,只有很少的时候他的信息会让你处在严重劣势——也就是说,maximin 所担心的那个最坏情况本身是小概率。第二,你的对手极不可能在执行任何接近最优的策略:毕竟如果这件事对你都这么难分析,对他也不会容易。他在脚注里补了一条自我提醒,方向正好相反:正因为对方可能打得不完美,从别人的行为里做推断有时是危险的,尤其当他们的偏好难以读懂时;他举的例子是伊拉克的大规模杀伤性武器——许多人确信武器存在,不是因为情报,而是因为他们相信萨达姆只要放核查人员进去、让他们什么也找不到,就能保住自己和政权。结论:对方的信息优势要按概率打折,对方的策略水平也要打折;但「从对方的行为反推」这件事本身同样要打折。
对照原文
Two rays of light creep into this gloomy situation: First, only rarely will his information put you at severe disadvantage. Second, it is extremely unlikely that your counterpart is playing anything close to an optimal strategy. After all, if it is so hard for you to analyze, it can hardly be easy for him.²⁸
定位:第 IV 节〈Drawing inferences from others〉,p.24,「Two rays of light」
第 5 步把交易拆成两个部件:绝对优势(双方都得益)与信息不对称(零和)。
这一步是整站的支点。作者说,把这些情形分解成两个部件是有帮助的。第一个部件是买方的,它让双方都受益——这就是通常意义上的贸易收益。他接着把它与站 04 连起来:在许多金融情形里,买方的绝对优势来自她的互补能力。例子是一块空地:在 A 手里可能远不如在 B 手里值钱,A 把它卖给 B,两人都因为绝对优势而获益。第二个部件是纯粹的信息不对称:如果 A 在赌英镑对美元下跌、而 B 在赌它上涨,那就不存在任何绝对优势,这里只有信息上的不对称——一方赚的正是另一方亏的。结论:判断一笔交易之前,先问这两个部件各占多少。
对照原文
It is helpful to break down these situations into two components. A potential buyer’s absolute advantage benefits both players. It represents the usual gains from trade. In many financial situations, as we observed above, a buyer’s absolute advantage stems from her complementary skills. An empty lot in A’s hands may be worth much less than it would be in B’s. Both gain if A trades to B, due to absolute advantage. But such an argument would not apply if A was speculating that the British pound would fall against the dollar when B was speculating that it would rise. There is no absolute advantage in such a situation, only information asymmetries.
定位:第 IV 节〈Absolute advantage and information asymmetry〉,p.25,「break down these situations into two components」
第 6 步纯信息不对称会走向无交易均衡;格言 C 是化解办法。
作者接着推演纯信息不对称的后果。前提是双方都认出这是纯粹的信息不对称局面。推演:那么只有更知情的那一方应当参与;而「既然你愿意交易,说明你知道些什么」这种恰当的推断,会把局面推向著名的。结论被写成格言 C:当信息不对称可能让对方担心与你交易时,向她指出你在哪些重要方面拥有绝对优势;你也可以指出她的绝对优势,但她多半已经知道了。作者随即把镜头转向买方:当你是买方时要当心,卖方声称的绝对优势可能是虚幻的。他给了三个例子:集市上的卖家擅长解释为什么你的特殊身份值得一个让他亏本的价格——比如今天收摊了、他得拿钱回家给老婆;嫌早高峰车声吵的卖房人可能撒一个不算谎的谎,说自己是要搬到离工作更近的地方,暗示这对你不重要,因此存在绝对优势;旅游区的商店永远在「清仓大甩卖」。他的收束句很硬:多数骗局之所以能成立,是因为被骗的那个人以为自己正在从别人手里占到便宜。作者随后用 Guys and Dolls 里 Sky Masterson 转述他父亲的话收尾:总有一天会有人拿出一副封条还没拆的新牌,跟你打赌他能让黑桃 J 跳出来往你耳朵里喷苹果汁;别接这个赌,否则你一定会落得一耳朵苹果汁。
对照原文
If both parties recognize a pure asymmetric information situation, only the better informed player should participate. The appropriate drawing of inferences of “what-you-know-since-you-are-willing-to-trade” should lead to the well known no-trade equilibrium. Understanding this often leads even ordinary citizens to a shrewd strategem:
Maxim C: When information asymmetries may lead your counterpart to be concerned about trading with you, identify for her important areas where you have an absolute advantage from trading. You can also identify her absolute advantages, but she is more likely to know those already.
When you are the buyer, beware; seller-identified absolute advantages can be chimerical. For example, the seller in the bazaar is good at explaining why your special characteristics deserve a money-losing price – say it is the end of the day and he needs money to take home to his wife. The house seller who does not like the traffic noise in the morning may palter that he is moving closer to his job, suggesting absolute advantage since that is not important to you. Stores in tourist locales are always having “Going Out of Business Sales.” Most swindles operate because the swindled one thinks he is in the process of getting a steal deal from someone else.
定位:第 IV 节〈Absolute advantage and information asymmetry〉,p.25,「Maxim C」
对照原文
If a game theorist had written a musical comedy, it would have been Guys and Dolls, filled as it is with the ploys and plots of small-time gamblers. The overseer of the roving craps game is Nathan Detroit. He is seeking action, and asks Sky Masterson – whose good looks and gambling success befit his name – to bet on yesterday’s cake sales at Lindy’s, a famed local deli. Sky declines and recounts a story to Nathan:
On the day when I left home to make my way in the world, my daddy took me to one side. “Son,” my daddy says to me, “I am sorry I am not able to bankroll you to a large start, but not having the necessary lettuce to get you rolling, instead I'm going to stake you to some very valuable advice. One of these days in your travels, a guy is going to show you a brand-new deck of cards on which the seal is not yet broken. Then this guy is going to offer to bet you that he can make the jack of spades jump out of this brand-new deck of cards and squirt cider in your ear. But, son, do not accept this bet, because as sure as you stand there, you're going to wind up with an ear full of cider.”
In the financial world at least, a key consideration in dealing with UU situations is assessing what others are likely to know or not know. You are unlikely to have mystical powers to foresee the unforeseeable, but you may be able to estimate your understanding relative to that of others. Sky’s dad drew an inference from someone else’s willingness to bet. Presumably Ricardo was not a military expert, but just understood that bidders would be few and that the market would overdiscount the UU risk.
定位:第 IV 节,p.25–26,「If a game theorist had written a musical comedy」
第 7 步关键不是你知道多少,是你相对于对方知道多少。
作者从 Sky 父亲的故事里提炼方法。前提是:在金融世界里,处理 UU 情形的一个关键考虑,是评估别人可能知道什么、不知道什么。推演:你不太可能拥有预见不可预见之事的神秘力量,但你可能有能力估计自己相对于他人的理解程度。Sky 的父亲正是从「对方愿意打这个赌」这件事里做出了推断;而 Ricardo 大概不是军事专家,他只是明白买家会很少、而市场会过度贴现那份 UU 风险。结论:把注意力从「我懂不懂这件事」转到「我相对于对面那个人懂多少」。
对照原文(本步用到的句子)
In the financial world at least, a key consideration in dealing with UU situations is assessing what others are likely to know or not know. You are unlikely to have mystical powers to foresee the unforeseeable, but you may be able to estimate your understanding relative to that of others.
定位:第 IV 节,p.26,「assessing what others are likely to know」
查看本段完整版(第 5 步)第 8 步第一张格子(概率未知):格言 D 说,评估相对知识就可能够了。
作者把读者放回普通人的位置:假设你既不是本事出众的 Buffett,也不是思路格外清楚的 Ricardo,只是一个时不时拿到机会与信息的普通投资者。前提:你的第一件事是判断这个决策会落进哪个方框。他先处理概率未知的情形,给出一张 2×2 的表,行是「你容易不容易估」,列是「别人容易不容易估」,四格分别是:A 难缠的市场、B 他们是冤大头、C Sky Masterson 的爸爸/你是冤大头、D Buffett 卖给加州地震局的再保险。推演:第一行是受欢迎且相对容易的,有两个理由——其一,你对自己相对于他人的知识多半判断得不错,就像一个大开发商在自己熟悉的本地市场里考虑交易那样,因此你能较好地判断自己更可能在 B 还是 A;其二,如果你在 B,优势在你手里。A 则是典型的厚金融市场,价格平均而言公允。第二行才是本文的主题:Buffett 知道自己在 D——保费极其有利,而对方掌握极端改变赔率的信息的可能性很薄;C 则是你知道得少、别人可能知道不少。作者说,处理「你觉得概率难估」这类情形的关键,是判断别人是否觉得容易。他补了一条警觉清单:留意对方更知情的迹象,比如一个聪明人给出过于有利的赔率;甚至更进一步——如果另一个精明方愿意下注,而他无从知道你觉得概率难估,你就该起疑,因为他理应拥有足以自保的私有知识。他自己承认这类推理会无限回归。结论就是:在双方都可能难以评估概率的情形里,评估你相对于对方(也许就是市场)的知识,就可能已经够了。
对照原文
Let us assume that you are neither the unusually skilled Buffett nor the unusually clear-thinking Ricardo. You are just an ordinary investor who gets opportunities and information from time to time. Your first task is to decide into which box an investment decision would fall. We start with unknown probabilities.
Investing with Uncertainty and Potential Asymmetric Information
| | Easy for Others to Estimate | Hard for Others to Estimate | |---|---|---| | Easy for You to Estimate | A. Tough markets | B. They’re the Sucker | | Hard for You to Estimate | C. Sky Masterson’s Dad, You’re the Sucker | D. Buffett’s Reinsurance Sale Calif. Earthquake Auth. |
The first row is welcome and relatively easy, for two reasons: (1) You probably have reasonable judgment of your knowledge relative to others, as would a major real estate developer considering deals in his home market. Thus you would have a good assessment of how likely you are to be in Box B or Box A. (2) If you are in Box B, you have the edge. Box A is the home of the typical thick financial market, where we tend to think prices are fair on average.
The second row is more interesting, and brings us to the subject matter of this paper. In Part V below, we will see Buffett sell a big hunk of reinsurance because he knew he was in box D. His premium was extremely favorable, and he knew that the likelihood of extreme odds-shifting information being possessed by the other side was thin. Box C consists of situations where you know little, and others may know a fair amount. The key to successfully dealing with situations where you find probabilities hard to estimate is to be able to assess whether others might be finding it easy.
定位:第 IV 节〈Competitive knowledge, uncertainty, and ignorance〉,p.26,「Investing with Uncertainty and Potential Asymmetric Information」
对照原文
Be sensitive to telling signs that the other side knows more, such as a smart person offering too favorable odds. Indeed, if another sophisticated party is willing to bet, and he can’t know that you find probabilities hard to estimate, you should be suspicious. For he should have reasonable private knowledge so as to protect himself. The regress in such reasoning is infinite.
Maxim D: In a situation where probabilities may be hard for either side to assess, it may be sufficient to assess your knowledge relative to the party on the other side (perhaps the market).
定位:第 IV 节,p.27,「Be sensitive to telling signs」
第 9 步第二张格子(状态未知):E 危险水域、F 低竞争,两格都带事后诸葛亮风险。
作者把情形推到更极端:连世界的状态都未知——比如给一项全新技术做天使投资,或者为基础设施承保长期的恐怖袭击风险。第二张 2×2 只有一行(「你未知」),两列是「别人已知」与「别人未知」,对应 E 危险水域与 F 低竞争,两格都标着事后诸葛亮风险。推演:在某些无知情形里,你可能有把握认定别人并不更清楚,那就是 F——多数投资者在这里被吓退,而 Buffett 们与当年的 Rothschild 们在这里赚了很多钱。投资者被吓退,是因为他们用一条启发式规则远离 UU 情形,理由是自己可能在 E,哪怕认真评估会告诉他们那种结果极不可能。此外两格都带着:作者列了三种不公平的事后指责——在无知中投资而结果不好时被责怪,尽管那是一个好决策遇上了坏结果;被指责没有考虑到别人可能知道得更多,而事实上他们并不知道;或者被指责没有考虑到别人可能知道得更多,而事实上他们确实知道,但这个负面因素被你的绝对优势带来的正面所压过。他说这些批评都不成立;但既然发生了重大亏损、而当时知识又稀薄,这笔投资在除最老练者之外的所有人看来事后都很愚蠢,而一个可能因此严重受损的投资者,完全可能被吓得不投。作者随即用这个想法重看 Gazprom:即便你是俄国专家,真正的俄国人几乎必然知道得比你多;那该怎么办?他给的谨慎路径是先评估自己的事后诸葛亮风险——它可能因为你那点「基本不相关」的专业而降低;如果这个风险可观,就走开;如果不大,而且俄罗斯内部人真的在投,那就利用这个方框、做那笔挎斗投资,而且你还有一个额外优势:很少有西方人会这么做,而他们才是你在 ADR 上的主要竞争者。整段的结论是:UU 情形因为信息不对称与缺乏竞争这两者的组合,而具有巨大的投资潜力。
对照原文
Let us now turn to the more extreme case, situations where even the states of the world are unknown, as they would be for an angel investment in a completely new technology, or for insuring infrastructure against terrorism over a long period.
Investing with Ignorance and Potential Asymmetric Information
| | Known to Others | Unknown to Others | |---|---|---| | Unknown to You | E. Dangerous Waters Monday Morning Quarterback Risk | F. Low Competition Monday Morning Quarterback Risk |
In some ignorance situations, you may be confident that others know no better. That would place you in Box F, a box where most investors get deterred, and where the Buffetts of this world, and the Rothschilds of yesteryear have made lots of money. Investors are deterred because they employ a heuristic to stay away from UU situations, because they might be in E, even though a careful assessment would tell them that outcome was highly unlikely. In addition, both boxes carry the Monday Morning Quarterback (MMQ) risk; one might be blamed for a poor outcome if one invests in ignorance, when it was a good decision that got a bad outcome; might not have allowed for the fact that others might have had better knowledge when in fact they didn’t; or might not have allowed for the fact that others might have had better knowledge, when in fact they did, but that negative was outweighed by the positive of your absolute advantage. The criticisms are unmerited. But since significant losses were incurred, and knowledge was scant, the investment looks foolish in retrospect to all but the most sophisticated. An investor who could suffer significantly from any of these critiques might well be deterred from investing.
定位:第 IV 节,p.27,「Investing with Ignorance and Potential Asymmetric Information」
对照原文
Let us revisit the Gazprom lesson within this thought in mind. Suppose you are a Russia expert. It is still almost inevitable that real Russians know much more than you. What then should you do? The prudent course, it would seem, would be first to determine your MMQ risk. It may actually be reduced due to your largely irrelevant expertise. But if MMQ is considerable, steer clear. If not, and Russian insiders are really investing, capitalize on Box E, and make that sidecar investment. You have the additional advantage that few Westerners will be doing the same, and they are your prime competition for ADRs.²⁹
Speculation 3. UU situations offer great investment potential given the combination of information asymmetries and lack of competition.
定位:第 IV 节,p.28,「revisit the Gazprom lesson」
核查:读到 Gazprom 那一段的最后一句「capitalize on Box E」时,很容易觉得它和前一段「F 才是 Buffett 们赚钱的方框」打架,这里说清楚:按作者自己在表里的定义,E 是「别人知道、你不知道」,F 是「别人也不知道」;而这一段的前提恰恰是「真正的俄国人几乎必然知道得更多」,所以 Gazprom 落在 E,原文没有写错。两格能赚钱的方式不同——在 F 你靠的是竞争稀薄,在 E 你靠的是挎斗:跟着那些确实更知情、而且真的在买的人。这也正是这一步要你先判断事后追责风险、再看「俄罗斯内部人是不是真在投」的原因。
第 10 步什么时候容易看出自己被当成冤大头:那些主动寄来的收购信。
作者在这一节的最后给了一个反方向的例子,前提是他刚说完 E 和 F 两格「大钱在这里易手」——既然别人会想占你便宜,那第一个要解决的问题就是:什么时候你能判断自己正被当成冤大头?他说有时候这很容易。任何持有小额油气权益的人都收到过许多主动寄来的收购信,开价无疑远低于公允价值。推演他写得很干脆:这些买家是买方垄断者,压低报价本来就是合理做法;他们甚至未必掌握任何内幕知识,但他们确实在占便宜——占的是冲动的人、不耐烦的人,以及那些不懂本文这些概念的人的便宜。他接着补了一层:可能当冤大头这件事本身也可以是优势,只要你能估出它的概率。人极其厌恶被背叛——当损失是由一个背叛你的人、而不是由无所谓的自然造成时,人们会要求强得多的赔率(作者与 Bohnet 2004 年的研究)。结论因此带一个反直觉的尾巴:正因为有背叛风险的地方人人退避,那里的潜在赔付会高于理性决策分析本来所需的水平。
对照原文
Boxes E and F are also the situations where other players will be attempting to take advantage of us and, if it is our inclination, we might take advantage of them. This is the area where big money changes hands.
A key problem is to determine when you might be played for a sucker. Sometimes this is easy. Anyone who has small oil interests will have received many letters offering to buy, no doubt coming from people offering far less than fair value. They are monopsonists after all, and appropriately make offers well below the market. They may not even have any inside knowledge. But they are surely taking advantage of the impulsive or impatient among us, or those who do not understand the concepts in this paper.
Being a possible sucker may be an advantage if you can gauge the probability. People are strongly averse to being betrayed. They demand much stronger odds when a betraying human rather than an indifferent nature would be the cause of a loss (Bohnet and Zeckhauser, 2004). Given that, where betrayal is a risk, potential payoffs will be too high relative to what rational decision analysis would prescribe.
定位:第 IV 节,p.28,「played for a sucker」
两张格子合成一张
| 别人容易估 / 别人已知 | 别人难估 / 别人未知 | |
|---|---|---|
| 概率未知 · 你容易估 | A.难缠的市场 典型的厚金融市场,价格平均而言公允 | B.他们是冤大头 优势在你这边 |
| 概率未知 · 你难估 | C.Sky Masterson 的爸爸/你是冤大头 你知道得少,别人可能知道不少 | D.Buffett 卖给加州地震局的再保险 保费极其有利,对方掌握改变赔率的信息的可能性很薄 |
| 状态未知 · 你未知 | E.危险水域 +事后诸葛亮风险 | F.低竞争 +事后诸葛亮风险;Buffett 们与当年的 Rothschild 们赚钱的地方 |
读表最快的办法:先定行(我估得动吗),再定列(别人估得动吗)。第一行你多半判断得准;第二行和第三行才是本文的主题,而且事后诸葛亮风险只出现在最后一行的两格里。
这一站的结论
先把绝对优势(双方都得益)和信息不对称(零和)分开,再决定要不要主动把自己的优势讲给对方听(格言 C)。判断该不该进场时,关键不是你知道多少,而是你相对于对方知道多少(格言 D);而多数人在最好的那一格里被吓退,是因为怕自己其实在隔壁那一格、也怕事后被追责。
想一想:回到 Gazprom。假设你是研究俄罗斯政治的专家,这个身份让你更该投,还是更不该投?
写下你的答案再展开
两个方向同时存在,而作者的排序很清楚。不利的一面:你是专家也不改变「真正的俄国人几乎必然知道得更多」,所以你仍然在第三行、偏向 E 那一格。有利的一面恰恰来自这份专业的「基本不相关」——它降低了你的事后诸葛亮风险,因为别人不会指责一个懂行的人没做功课。所以作者的顺序是:先评估事后诸葛亮风险,大就走开;不大且俄罗斯内部人真在投,就做那笔挎斗投资,而且西方人少这件事本身是优势。见本站第 9 步。
边界:格子能做什么,不能做什么
- 两张格子是分类工具,不是概率模型。它帮你问对问题(「别人估得动吗」),不给你任何数值。
- 事后诸葛亮风险的大小取决于你的身份:受托人、基金经理与自有资金的个人投资者面对的后果完全不同,本文没有区分。
- 作者在这一节还提到「被当冤大头也可能是优势」(因为人极度厌恶被背叛,有背叛风险的地方赔付会被抬高)。这条是支撑性的观察,本课未在正文展开,原文在第 28 页。
下一站:把优势、知情概率与选择因子放进同一个式子——作者的 (1) 式与格言 E。
09 / 优势倍数与选择因子
优势倍数抵不抵得过选择效应:(1) 式与格言 E
第 1 步三个参数:优势倍数 a、对方知情的概率 p、他知情时的选择因子 s。
作者先说明为什么需要一个式子。前提是站 08 结尾那个两难:你处在 UU,对方可能知情,而你通常不知道他到底知不知情。他先驳回一条赌徒格言——「如果你看不出谁是冤大头,那你就是冤大头」——说它在 UU 投资里不自动成立,理由有两条:第一,对方也可能不知情,比如你买一个半拉子的购物中心,开发商可能真的只是钱花完了(那是他给出的解释),而不是发现了租户意愿很差;第二,你可能有互补能力,比如与沃尔玛关系很好,这会给你一个显著的绝对优势倍数。然后他建模,并且明说这是简化:撇开风险厌恶与资金管理,再按 BS 的设定假设你能给出一个可信的、要么接受要么走人的出价 1。资产对他的价值是 v,一个未知量;对你的价值是 av,这个 a 就是你的。你对 v 的主观先验分布是 f(v),先验均值 m 小于 1(他在脚注里说明这一条很重要:否则如果卖方不知情,他会拒绝你的出价)。于是三个参数描述了这个局面:优势倍数 a;对方知情的概率 p;以及他知情时对你的 s——s 是「当对方知情、因而只在资产对她价值低时才卖」的条件下,平均而言你能拿到的期望价值的比例。作者加了一句关键的限定:鉴于这是 UU 情形,你并不知道 s,但你应当依赖你对这个参数的主观分布的均值。
对照原文
Though you may confront a UU situation, the party or parties on the other side may be well informed. Usually you will not know whether they are. Gamblers opine that if you do not know who the sucker is in a game that you are the sucker. That does not automatically apply with UU investments. First, the other side may also be uninformed. For example, if you buy a partially completed shopping center, it may be that the developer really did run out of money (the proffered explanation
for its status) as opposed to his discovery of deep tenant reluctance. Second, you may have a complementary skill, e.g., strong relations with WalMart, that may give you a significant absolute advantage multiple.
Let us simplify and leave risk aversion and money management matters aside. Further posit, following BS, that you are able to make a credible take-it-or-leave-it offer of 1. The value of the asset to him is v, an unknown quantity. The value to you is av, where a is your absolute advantage. Your subjective prior probability distribution on v is f(v). The mean value of your prior is m < 1.³⁰ In a stripped-down model, three parameters describe this situation: your advantage multiple, a; the probability that the other side is informed, p; and the selection factor against you, s, if the other side is informed.³¹ Thus s is the fraction of expected value that will apply, on average, if the other side is informed, and therefore only sells when the asset has low value to her. Of course, given the UU situation, you do not know s, but you should rely on your mean value of your subjective distribution for that parameter.
定位:第 IV 节〈The advantage multiple versus selection formula〉,p.28–29,「three parameters describe this situation」
第 2 步两个极端先看:p = 0 时 am > 1 就出价;p = 1 时要 ams > 1。
作者用两个端点把式子的含义先固定下来。前提是三个参数的定义已经给出。推演:如果你知道 p = 0,也就是对方知道的并不比你多,那么只要 am 大于 1 你就该出价——你付出 1,拿到的期望价值是 a 乘以 m。如果你知道存在选择,也就是 p = 1,那么你应当在「你的倍数足够补偿选择效应」时投资,即 ams > 1。结论:两个端点之间的所有情形,就是下一步那个一般式要处理的。
对照原文
If you knew p = 0, that the other side knew no more than you, you would simply make the offer if am > 1. If you knew there were selection, i.e., p = 1, you would invest if your multiple more than compensated for selection, namely if ams > 1. The general formula is that your return will be:
定位:第 IV 节〈The advantage multiple versus selection formula〉,p.29,「If you knew p = 0」
第 3 步一般式 (1):回报 = am[ps + (1−p)·1],大于 1 就出价。
作者把两个端点合成一个式子。前提是 p 介于 0 与 1 之间,而两种情形下你拿到的期望价值不同:对方知情时是 ams,对方不知情时是 am。推演就是按 p 加权:你的回报是 am[ps + (1−p)1],这就是原文编号的 (1) 式。结论是一条判据:当 (1) 式的值超过 1 时你应当出价——因为你付出的正是 1。把两个端点代回去检验:p = 0 时括号里等于 1,式子退化成 am;p = 1 时括号里等于 s,式子退化成 ams。两个端点都对上了。
当前替代值(a=5、m=0.9、p=0.05、s=0.5):5 × 0.9 × (0.05×0.5 + 0.95) = 4.39
对照原文
am[ps + (1-p)1] .
(1)
Following Maxim E, you should make your offer when the expression in (1) exceeds 1.
定位:第 IV 节〈The advantage multiple versus selection formula〉,p.29,「am[ps + (1-p)1]」
第 4 步格言 E:显著的绝对优势对选择效应提供保护——除非两个条件同时成立。
前面三步是推导,这里是作者编号的格言。 说:一个显著的绝对优势对潜在的选择效应提供了某种保护;在 UU 世界里,如果你的优势倍数很大,你就应当投资——除非对方知情的概率很高,而且除此之外预期的选择因子还很严重。本课注这句话的语法值得停一下:两个「除非」是并列的,必须同时成立才推翻结论,不是任一条。作者的结论句是操作性的:按照格言 E,当 (1) 式的值超过 1 时就给出你的出价。
对照原文
Maxim E: A significant absolute advantage offers some protection against potential selection. You should invest in a UU world if your advantage multiple is great, unless the probability is high the other side is informed and if, in addition, the expected selection factor is severe.
定位:第 IV 节,p.29,「Maxim E」
第 5 步实际可选出价 t,选择因子随 t 变,于是 (2) 式。
作者放松「出价固定为 1」这个简化。前提是现实里你可以选择出多少。推演:于是 s 会随 t 变化,写成 s(t);在这种情形下,任何 t 的收益是 am[ps(t) + (1−p)1] − t,这就是 (2) 式。结论:如果在最优出价 t* 处这个量为正,你就该出 t*。他在脚注里补了一个技术条件:如果先验分布是齐次的(比如从 0 开始的均匀分布或三角分布),s 的值会保持不变。
对照原文
In practice, you will have a choice of offer, t. Thus, s will vary with t, i.e., s(t).³² The payoff for any t will be
am[ps(t) + (1-p)1] - t. (2)
If at the optimal offer t*, this quantity is positive, you should offer t*.
定位:第 IV 节,p.29–30,「am[ps(t) + (1-p)1] - t」
第 6 步现实里不是一次报价:UU 买方触发不了展开论证,卖方于是做选择性披露。
作者自己指出这个模型的表述不够写实:它假定了一次性报价、没有沟通。事实上多数重要的金融交易有多轮微妙的来回,而这不只是空话——有时会提供真实信息(财务报表、地质报告、古董鉴定),出价本身也会泄露信息;而且双方都明白,信息不对称对双方都是敌人,就像任何委托代理问题一样。推演分两段。第一段是理想情况:众所周知,如果披露的信息可以被验证,而且买方知道哪些维度上的信息有用,那么通过一个,所有信息最终都会被披露——考虑一个取值在 1 到 100 之间的一维情形:手里是 100 的卖方必定披露,这意味着最好的未披露值是 99;于是 99 也会披露,如此一路下到 2。第二段是买方处在 UU 时:展开不会发生,因为他不知道相关的维度是什么;卖方会把不利信息留在买方不知道的维度上,做——宣扬有利的,压下不利的。结论带着代价:这场「优势倍数对选择效应」的博弈通常会这样进行——卖方解释自己为什么没有私有信息,或者披露一些表明 m 与 a 都很大的私有信息;但许多本可成交的有利交易仍然做不成,因为不那么知情的一方无法评估自己不知道的东西。当共同价值信息上存在不对称、或者像几乎所有 UU 情形那样被怀疑存在不对称时,事前双方都受损。
对照原文
Our formulation posited a take-it-or-leave-it offer with no communication. In fact, most important financial exchanges have rounds of subtle back-and-forth discussion. This is not simply cheap talk. Sometimes real information is provided, e.g., accounting statements, geological reports, antique authentications. And offers by each side reveal information as well. Players on both sides know that information asymmetry is an enemy to both, as in any agency problem.
It is well known that if revealed information can be verified, and if the buyer knows on what dimensions information will be helpful, then by an unraveling argument all information gets revealed.³³ Consider a one-dimension case where a value can be between 1 and 100. A seller with a 100 would surely reveal, implying the best unrevealed information would be 99. But then the 99 would reveal, and so on down through 2.
When the buyer is in a UU situation, unraveling does not occur, since he does not know the relevant dimensions. The seller will keep private unfavorable information on dimensions unknown to the buyer. She will engage in signposting: announcing favorable information, suppressing unfavorable.³⁴
The advantage multiple versus selection game will usually proceed with the seller explaining why she does not have private information, or revealing private information indicating that m and a are large. Still, many favorable deals will not get done, because the less informed party can not assess what it does not know. Both sides lose ex ante when there will be asymmetry on common value information, or when, as in virtually all UU situations, asymmetry is suspected.
定位:第 IV 节〈Playing the advantage multiple versus selection game〉,p.30,「unraveling does not occur」
试一试:固定优势,把知情概率和选择因子一起拖,看曲线什么时候跌破 1
这里配可拖模型,是因为格言 E 的「除非…而且…」是一个联合条件,文字只能说方向,说不出边界在哪。拖动之前先回答:把优势倍数固定在刚好过 1 的水平,知情概率要多高,(1) 式才会跌破 1?把这个式子搬到自己的例子上时,最容易漏掉的是 s——它必须单独赋一个值,默认它等于 1 就等于假设「就算对方更知情,他也不会挑着卖给我」。
(1) 式的回报(大于 1 则出价)
读图:横轴是对方知情的概率 p(0 到 100%),纵轴是 (1) 式的回报,虚线是 1,也就是出价的盈亏分界。曲线的左端点是 am,右端点是 ams。这是教学演算,四个参数都是你输入的信念,不是观测值。
这一站的结论
不要因为「对方可能更知情」就退出。把三件事同时摆出来:你的优势倍数有多大、他知情的概率有多高、他知情时你成交到的东西还剩多少价值;只有后两者共同不利到能把 am 压到 1 以下时,才该走开。而且要记住:你处在 UU 时,卖方不会被逼着全盘披露,他只会宣扬有利的那些维度。
边界:这个式子省掉了什么
- 作者自己说这是「简化」:撇开了风险厌恶与资金管理,也假设你能给出一个可信的、要么接受要么走人的出价。
- (2) 式按原文的写法是「期望价值减出价」,没有再乘一次成交概率。用它比较不同的 t 时要记住这一点——站 07 的模型里那条曲线是乘过成交概率的,两处的口径不同。
- s 在 UU 情形里是不知道的。作者说用你主观分布的均值代替;把滑块拖到某个 s,是你在表达一个判断,不是在观察一个事实。
下一站:从这里开始,正文就是作者的英文原文,讲解改成段前引导与段后批注。
10 / 拍卖里的未知规则
拍卖里的未知规则
第 1 步拍卖的通常处方是卖方披露共同价值信息,以消除赢家诅咒。
这一步作者在回答:教科书里的拍卖建议是什么,它假设了什么。上一站刚说完,UU 买方触发不了展开论证,卖方于是只做选择性披露;拍卖正好是检验这件事的场地。作者先给出标准图景(知情卖方对一群不那么知情的买方),再给出标准处方(卖方主动披露)。读原文时盯住第二段里「worth roughly the same to all」这个限定——赢家诅咒只在共同价值的场合成立,这个条件后面会被打破。
术语 「communications spectrum」指电信频谱;美国自 1994 年起用拍卖分配它,是把拍卖理论推向实务的标志性案例。
补全推理 这一段末尾的 The 与下一段的 usual prescription 是同一句话——原文在这里翻页了。
定位:第 IV 节〈Auctions as UU games〉,p.30,「Auctions have exploded」
术语 :当一件东西对所有人价值大致相同时,出价最高的人应当意识到其他所有人都认为它更便宜,因此自己的估计偏高了。
联系 这和站 07 是同一件事的另一副面孔:在 BS 里「成交」告诉你卖方的价值低,在拍卖里「你赢了」告诉你所有人的估计都比你低。
定位:第 IV 节〈Auctions as UU games〉,p.31,「concerns about the Winner’s Curse」
第 2 步现实拍卖连规则都可能未知。
这一步作者要把「不知道别人的出价」升级成「不知道游戏的规则」。前一步的处方假设规则清楚、只有信息不对称;这一段说,连这个假设都常常不成立。读原文时注意他举的两个场景——热门房市里的房屋出售、以及公司出售——以及那个具体的失望时刻:赢家以为一轮定胜负,却被告知还有「最佳最终报价」轮。接着的一段会给出一个五天的真实例子。
术语 这类「拍卖与谈判交替、规则随时可变」的流程,作者与 Subramanian 称为(见原文脚注 35)。
旁注 作者顺带限定了范围:他说的是「当代常见的拍卖现象」,在房屋与公司出售中最常见,不是所有拍卖都这样。
定位:第 IV 节〈Auctions as UU games〉,p.31,「Even the rules of the game may not be known」
补全推理 这里有一步没写出来:投资银行只对 P&G 说「必须大幅提高」,而对 Gillette 几乎什么也没说。在一个规则不透明的流程里,「银行没跟我说什么」本身就是信号——Gillette 由此推断自己远高于其他人。
联系 美林周五一早才要更多尽调材料并要求延到周一。作者特意加了一句限定:Gillette 有好几个月时间可以早问。这句旁注是在提示:这个动作更像战术拖延,不像真的需要材料。
补全推理 最后那句反问是整段的落点:如果 Gillette 那天出 33.50,会不会有第三轮?连「有没有下一轮」这件事都取决于卖方当时的临场决定,这就是「规则未知」的确切含义。
定位:第 IV 节〈Auctions as UU games〉,p.31,「a “no one knows the rules” process ensued」
第 3 步Recovery Engineering 的五天:不只出价未知,连对方为什么消失都未知。
这一步作者从流程转向对手方的动机。前一段留下的问题是「Gillette 怎么了」,他在这里给出董事会当时的猜测,以及后来才知道的事实。读原文时注意两层不可知的叠加:既不知道对手的策略,也不知道对手的处境。最后那句「Not unusual」是作者的判断,不是叙述。
补全推理 Gillette 的推理是:既然周一之后没人叫我加价,说明我已经远高于其他人;那就不如等交易公布后再加一点,而不是现在就多出一截。
定位:第 IV 节〈Auctions as UU games〉,p.31,「What happened to Gillette」
联系 这正是站 08 第 3 步那条「两线光明」的第二条:对手极不可能在执行接近最优的策略。Gillette 的消失不是高明的博弈,而是它自己出了问题。
旁注 作者在脚注里补了一句:Recovery 在与 P&G 的协议里放了一笔随收购溢价递减(最终降到 0)的分手费,用来抬高任何交易后的竞价。
定位:第 IV 节〈Auctions as UU games〉,p.32,「Gillette never came back」
核查:原文写「the $300 million deal concluded」。当时的公开报道给出的成交总额约为 2.65 亿美元;本课未取得逐股价格的原始文件,因此并列两个数字,不改写原文。这个数字不影响作者的论点——他要说明的是规则与策略都不可知。
第 4 步花旗买广发:如果别人也打不开那个口袋,买一头袋中猪可能非常划算。
这一步作者把同一个结构放大到跨国交易上。前面两个例子里,不确定的是规则与对手;这一个例子里,连「赢到的是什么」都不确定——《纽约时报》的说法是花旗赢得的是「与该行谈判购买股权的权利」。读原文时盯住最后一句的条件从句「if others also can not open the bag」——这正是站 08 第二张格子里的 F 格,也是猜想 3 的完整表述。
术语 「won the right to negotiate」——赢得的是谈判权,不是股权。在一场规则未定的出售里,这是常见的中间状态。
联系 花旗的判断正是格言 D 的用法:它不需要知道这家银行值多少,只需要相信自己相对于其他竞标者并不更无知。
补全推理 最后一句里有一个没写出来的条件:「买一头袋中猪」之所以可能划算,前提是价格已经反映了所有人打不开袋子这件事——也就是猜想 1 说的那个低价。
定位:第 IV 节〈Auctions as UU games〉,p.32,「Citigroup made the winning bid」
这一站的结论
规则未知、策略未知是常态,不是意外。在这种局里,你不需要知道那件东西值多少;只要有把握认定别人也不比你更知情,「别人也打不开那个袋子」本身就是一项可交易的优势。
下一站:赔付结构本身也是一个 UU 决策——格言 F 与一封几乎不给信息的信。
11 / 把回报放在资产值钱的时候
把回报放在资产值钱的时候:格言 F 与 Davis Oil
第 1 步UU 里连赔付水平相关的事件都难预见,所以通常按钱分饼。
这一步作者换了一个角度:前面九站问的都是「该不该投」,从这里开始问「按什么结构拿回报」。前提是站 01 立下的那条——UU 意味着连状态清单都列不出来,所以以事件为条件的合同写不出来。读原文时注意最后半句的转折:这看起来简化了问题,但作者说老练的投资者仍然常常搞混。下一段给出他们搞混的具体样子。
补全推理 「按收到的钱而不是按发生了什么来分饼」意思是:合同只写「收入到多少时怎么分」,不写「如果技术突破了怎么分」——因为后者列不全。
定位:第 IV 节〈Ideal investments with high and low payoffs〉,p.32–33,「depend not on what actually happens」
第 2 步VC 的强制稀释融资把份额加在公司最不值钱的时候,方向正好反了。
这一步是上一步说的「搞混」的具体案例。作者先描述现行做法(破产时的全部资产请求权、业绩不佳后的强制稀释融资),再给出它在理论上的辩护,然后逐条拆掉这个辩护。读原文时盯住 In reality 这个转折词,以及 Worse still for the VCs 这句——他最后要说的不是「这对创始人不公平」,而是「这对投资人自己也不划算」。
术语 :初创公司业绩不佳后常见的一轮融资,条款让既有投资人的持股比例大幅提高。
补全推理 「奖励管理层在低谷时赌博」这一步没有展开:份额被大幅稀释之后,管理层手里的股权只有在极端好结果下才值钱,于是他们理性地会去搏极端结果。
联系 这一段末尾的 when 与下一段开头的 company is not worth much 是同一句话——原文在这里翻页了。
定位:第 IV 节〈Ideal investments with high and low payoffs〉,p.33,「“cram down” financings」
补全推理 作者给出的替代方案是把方向反过来:结果差时投资人让出份额,公司特别好时投资人增加份额。下一段的格言 F 正是这条建议的一般形式。
定位:第 IV 节,p.33,「they sacrifice ownership share if matters turn out poorly」
第 3 步格言 F:目标是在资产价值高的时候拿到好赔付。
这一步是作者编号的第六条格言,也是本站的落点。前两步给的是负面例子(份额加错了地方),这一步给出正面的一般规则。读原文时注意格言的两半:前半是诊断(连老练投资者也低估价值的变动幅度),后半是处方(把好赔付放在价值高的那一侧)。紧接着的一段用 Ricardo 说明这条规则不需要你能预测方向。
术语 :注意它说的是赔付结构,不是方向判断。
定位:第 IV 节,p.33,「Maxim F」
补全推理 这里的推理是:Ricardo 不需要判断拿破仑会不会输。他只需要注意到,在英国获胜的那个世界里,他赢到的英镑本身也更值钱;而在战败的世界里,他亏掉的英镑更不值钱。赔付的不对称来自货币的购买力,不来自概率。
联系 这一句同时回收了站 03 第 5 步的百分比对称:大波动之所以是「友」,正是因为上下两侧的价值不对称。
定位:第 IV 节,p.33,「No doubt Ricardo also took Maxim F into account」
第 4 步Davis Oil:一封几乎不给信息、连抬头纸都不用的信。
这一步作者把格言 F 放进一道要你先作答的决策题。前提是前三步给的判据;现在他给你一封真实的信,要你在读他的答案之前先决定。读原文时注意四条事实:你没听说过这家公司、信是突然来的、你的权益来自 Davis 买走了邀你入伙的朋友的管理合伙人权益、以及 Davis 依法必须给你这个选择。最后一句是作者的要求:先决定投还是只等那份免费的权益金,再往下读。
术语 :不出钱参与钻井,把权益交给作业方,只留一小笔与生产挂钩的收入分成。
旁注 作者在脚注里说明,那位邀他入伙的朋友是 Northwest Oil 的总裁 Malcolm Brachman,他的桥牌队友与好友;而 Malcolm 此时已经过世——一个后果是,他无法再给作者建议。这句旁注很关键:它把「可以问人」这条路也堵死了。
联系 Exhibit A 的信件全文在原文第 34 页,是一张扫描件;本课把它逐字转录后放在原文全文站,可以从这里跳过去看。
定位:第 IV 节〈A UU investment problem〉,p.33,「Look at the letter in Exhibit A」
第 5 步作者怎么做的:从对方的行为反推信息,再打一个电话把赔率问出来。
这一步是作者自己的答案,也是全篇最完整的一次方法演示。前一步把你放在信息极度贫乏的位置;这一步展示他如何在不增加地质知识的情况下改善判断。读原文时分两段看:第一段是纯推断(对方为什么这样写信),第二段是一个电话(把历史基准率问出来)。注意最后那句 The clinching argument——决定他下手的不是地质,是对方的一个礼貌提议。
补全推理 这段推理有三跳:Davis 无法排除他 → Davis 也不需要他这点钱 → 那么这封几乎不给信息、连抬头纸都不用的信,最可能的解释是「想劝退」。再加一跳:Davis 花了不少力气才决定钻,说明它自己看好。
联系 这正是站 08 第 2 步说的:对方仅仅通过「怎么开价」就在使用你没有的信息——这里是通过「怎么写信」。
定位:第 IV 节〈A UU investment problem〉,p.35,「Here is what your author did」
术语 :在没有已知油气构造的区域打的探井。对方说「无法猜测成功概率」,这是真话,但不等于没有基准率。
补全推理 这是整段的方法要点:问不出这一口井的概率,就问历史频率。20–25% 的成功率与成功时 10 比 1 的赔付,合起来的期望值约为本金的 2 到 2.5 倍——再加上「只有现在参与才有权成为未来合伙人」这个上行期权。
联系 对方主动提出「我们很乐意接下你的权益、给你免费权益金」,等于第二次重复那封无抬头信的信息。作者把这个动作读成价值信号:Davis 越想把你劝走,这口井对它越值钱。
旁注 括号里的数字是作者事后才查到的:免费权益金只有收入的 1%,而参与则是 76%——这个对比信里没写。
定位:第 IV 节〈A UU investment problem〉,p.35,「he called Bill Jaqua」
第 6 步Davis 反转了通常的把戏:它刻意放大 UU 的一面来劝退你。
这一步是本站的收束,也是全篇关于「对方行为即信息」的最强表述。前面五步给的是一个案例;这一步把案例提炼成一条可迁移的观察。读原文时注意 reversed the usual ploy 这个说法——通常是有信息优势的人装无辜,这里是有信息优势的人故意把局面说得更不可知。这两种做法指向同一个动作:看对方想把你推向哪边。
联系 与站 08 第 5 步的格言 C 正好互为镜像:格言 C 教你主动讲出自己的绝对优势好让对方敢成交;Davis 做的是反面——它不想要你成交,所以它把 UU 的一面放大。
旁注 作者在后一节的复盘里说,三笔投资中 Gazprom 在六个月里表现不错,另外两笔(Tengion 与 Davis Oil)的结果当时都还没有定。
定位:第 IV 节〈A UU investment problem〉,p.35,「Davis was in a tough situation」
第 7 步复盘:三道决策题的结果,以及作者要你回去做的事。
这一步是第 IV 节的收尾,作者把前面抛给你的三道题收回来。前提是你已经在站 04 与本站各作过一次决定(Tengion、Gazprom、Davis Oil),而且在站 05 做过那份过度自信问卷。读原文时注意他给结果的方式:只有 Gazprom 有结论,另外两笔当时都还没定——他要你复核的是决策过程,不是结果。
联系 过度自信问卷的答案在原文脚注 41 里:1) 173,710 2) 2,716 3) 2,007,901 4) 130,119 5) 13 6) 12,212,000 7) $259B 8) 13.45% 9) 853,000。对照站 05 第 3 步:理论上应当只有约 2% 的真值落在你的意外点之外。
定位:第 IV 节〈Review of the bidding〉,p.35,「Go back now and grade yourself」
旁注 三笔的结果状态:Gazprom 在六个月里表现不错(站 04 第 7 步引的脚注 10 给了数字:2006 年 1 月 6 日提出时 33.60,九个月后付印时 47 美元);Tengion 与 Davis Oil 在作者写作时都还没有结果——Davis 那口井当时甚至还没开钻。
补全推理 作者要你回去重做的不是结论,而是过程:你当时用的是不是本文的原则。这正是全篇的验收方式——好决策与好结果是两回事,这一点从站 02 第 5 步的桥牌类比开始就在铺垫。
定位:第 IV 节〈Review of the bidding〉,p.35,「You were asked about three investments」
Davis 给的两个选项
| 选项 | 你出什么 | 你拿什么 | 信里写了没有 |
|---|---|---|---|
| ① 参与钻井 | 按比例分摊井的成本(信里给的估算:干井成本 $6,869,100,完井成本 $2,745,400) | 收入的 76%(作者事后算出) | 成本写了;76% 没写 |
| ② 不参与,交出权益 | 不出钱 | 收入的 1%(作者事后查到) | 信里只写「按 75% 净收入权益交割」;1% 这个结果没写 |
| 时限 | 收到提案后 15 天 | 逾期不回复视为选择② | 写了 |
读表最快的办法:看最后一列。信里写清楚的全是成本和时限,而两个选项的实际收入差了 76 倍——这正是作者说「这封信的目的是劝退」的证据。
这一站的结论
在 UU 情形里,对方为劝退你所做的动作,本身就是关于价值的信息。而在赔付结构上,即使你说不准会涨会跌,仍然可以把好赔付放在资产值钱的那一侧——Ricardo 买滑铁卢债券时想的正是这件事。
边界:这个案例能推广到什么程度
- 20–25% 的成功率与 10 比 1 的赔付都来自作者与对方联系人的一次电话,没有公开数据可核;页面按「原文这么说」呈现。
- 作者写作时这口井还没开钻,结果未定。这个案例检验的是决策过程,不是结果。
- 「对方想劝退我,所以这件事很值钱」是一条推断,不是定律。它成立的前提是对方确实不需要你的钱、也确实无法排除你——这两条在原文里都被明确说出来了。
下一站:同样的判据,换成 10 亿美元的一层再保险。
12 / Buffett 与加州地震局
Buffett 与加州地震局:格言 G、H 与全文结论
第 1 步加州地震局出到精算价值的五倍,纽约金融界无人接:a = 5,p 接近 0。
这一步作者把站 09 的 (1) 式放进一个真实的数字里。前提是格言 E 的判据:优势倍数大就该投,除非对方知情概率高且选择因子严重。读原文时把三个参数一一对上——五倍保费对应 a = 5,「投保方掌握大地震将至的内幕极不可能」对应 p 接近 0。注意作者是在现场听说这件事的,下一段他自己也去抢了。
术语 的「一层」有起点也有上限:在累计承保损失超过 50 亿美元之后才触发,这一层最多赔 10 亿美元。
术语 是按预期赔付算出的成本;「出到五倍」意思是保费是预期赔付的五倍。
联系 这句话就是 p 的取值理由:买保险的是地震局自己,它不可能掌握「大地震将至」的内幕。对照站 09 第 2 步的端点情形——p = 0 时 (1) 式退化成 am,判据只剩「优势够不够大」。
定位:第 V 节〈A Buffett Tale〉,p.36,「a $1 billion slice of reinsurance」
旁注 「还差 9.999 亿美元」是作者的自嘲,也是一条实质信息:这类机会即使被认出来,多数人也没有承接它的规模——这正是站 03 第 6 步说的「不易放大」。
定位:第 V 节〈A Buffett Tale〉,p.36,「My dinner table syndicate swung into action」
第 2 步Buffett 自己的说法:全部自留,最坏情况税后不超过 6 亿美元。
这一步是 Buffett 在 1996 年致股东信里的原话,作者整段引用。前一步给了外部视角(五倍保费、无人接单),这一步给内部视角(他怎么向股东解释)。读原文时盯住三个数:不超过 6 亿美元、不到账面价值的 3%、不到市值的 1.5%。最后一句是他的参照系——证券市场给伯克希尔带来的波动比这大得多。
术语 「retained all the risk for our own account」意思是不再往外分保——这一层的全部风险留在伯克希尔自己账上。
补全推理 这三个数是在回答一个没被问出口的问题:「万一真赔了怎么办?」他的答案不是「不会赔」,而是「赔了也扛得住,而且这个幅度比市场平常给我们的波动还小」。
联系 这正是站 06 第 6 步格言 B 的实践:优势大就投得多,但投多少要与自己的承受能力一起算。
定位:第 V 节〈A Buffett Tale〉,p.36,「a policy for the California Earthquake Authority」
联系 「与多数保险不同,投保方掌握自身风险内幕的可能性极低」——这一句是本篇把 p 与常规保险区分开的关键:车险与寿险里投保人几乎总是更知情,地震再保险里不是。
补全推理 作者在这里给华尔街的退缩列了三个可能的原因,一个比一个尖锐:不擅长承担难以估计的风险、没意识到所有人用的是同一个概率、或者只是担心被事后追责。第三条把我们带回站 08 的那一格。
定位:第 V 节〈A Buffett Tale〉,p.36–37,「beyond its dramatic overpricing」
第 3 步他怎么估概率:不知道,也不认为模型有用。
这一步回答一个自然的疑问:既然是 UU,Buffett 凭什么定价?前提是站 09 的 (1) 式并不要求你知道真实概率,只要求你判断相对知识。读原文时注意他的否定是双重的——既不知道真实赔率,也不认为计算机模型能帮忙;理由不是模型算得不准,而是它们宣称的精度本身是幻象,会制造虚假的安全感。作者随后把这段话翻译成一句对华尔街说的话。
补全推理 这一句是引文的引子:作者要证明的不是「Buffett 算得更准」,而是「Buffett 承认算不出来,仍然敢下手」。
定位:第 V 节〈A Buffett Tale〉,p.37,「approach to assessing the probabilities」
术语 「portfolio insurance」(组合保险)是 1980 年代流行的一种用程序化卖出来对冲下跌的策略,被广泛认为加剧了 1987 年的崩盘。
联系 这正好回到站 03 第 4 步:1987 年那次崩盘不是用平常解释市场波动的因素能解释的——厚尾与怪原因。
定位:第 V 节〈A Buffett Tale〉,p.37,「we believe the precision they project is a chimera」
联系 这句话与站 06 第 1 步正好构成一对:数学高手进场的领域超额回报消失,而数学高手算不出来的领域超额回报留存。
旁注 作者接着补了 2006 年的飓风保险:价格高达一年前的 20 倍,有些保单的保费等于最大潜在赔付的一半;Buffett 说「只要价格合适,我们会比任何人做得多……我们当然愿意在单一事件上亏 60 亿美元」。
定位:第 V 节〈A Buffett Tale〉,p.37,「Even if you hire 100 brilliant Ph.D.s」
第 4 步格言 G 与格言 H:为模糊打折要克服;别因为自己不知道就假设别人知道。
这一步是作者最后两条格言,它们从前三步的故事里直接长出来。前提是:华尔街的退缩既来自模糊厌恶(站 05 第 7 步),也来自「我不懂所以别人一定懂」的推理。读原文时注意两条格言的分工——G 针对你对不确定性的情绪反应,H 针对你对别人的错误推断。格言 H 的最后半句是全篇最强的行动主张,也是唯一一次作者说「有时值得赌」。
术语 :作者把它类比成暴食——是一种要克服的自然倾向,不是要消灭的错误。
定位:第 V 节,p.38,「Maxim G」
术语 :注意它没有叫你忽略信息劣势,而是叫你先估计它的大小。
联系 「评估他们是否可能比你知道得多」就是格言 D 的相对知识,「赔率极其有利时值得赌」就是格言 E 里那个 (1) 式大于 1。八条格言在这里合拢。
旁注 作者随后用同一套逻辑解释 Buffett 2006 年的捐赠:把钱交给盖茨基金会是「挎斗慈善」,因为 Gates 的创造力、远见与务实是互补能力,在慈善里和在商业里一样值钱。
定位:第 V 节,p.38,「Maxim H」
第 5 步全文结论:UU 里的清晰思考,收益可能远大于普通场合。
这一步是论文的结论一节,作者先自贬再给判断。前提是前面十二站的全部内容;他在这里承认这些内容的证据地位。读原文时注意他自己列的三条限制:猜想多于结论、轶事多于确定数据、理论常常是试探性和隐含的。然后才是那句判断——正因为竞争有限、价格严重偏离,这里的回报可能远大于普通场合。
旁注 这三句自我限定是全文最重要的边界声明:本课把它留在正文里,因为它是作者自己的话,不是课程加的提醒。
补全推理 这里有一个条件从句常被略过:clear thinking 的收益要先「If they do improve」——也就是说,作者主张的是「清晰思考可能大幅改善这类决策」,不是「UU 投资一定赚钱」。
定位:第 VI 节〈Conclusion〉,p.38,「more speculations than conclusions」
联系 「只算主要影响个人的那些」回到站 02 第 1 步:个体的不可知远比总体的多,而且新闻不会报道它们。
旁注 最后一句是全文的标题句,也是摘要的末句:学会在 UU 世界里更明智地投资,可能是显著提升你富裕程度最有希望的途径。
定位:第 VI 节〈Conclusion〉,p.38,「How important are UU events」
这一站的结论
学会在 UU 世界里更明智地投资,可能是显著提升富裕程度最有希望的途径——但前提是两句话一起用:承认自己不知道(不要假装模型能算出来),同时不假设别人知道(先估计他们的相对知识,再决定折不折价)。
边界:一个成功案例能证明什么
- 一笔成功的交易不构成策略证据。作者自己在结论里说,本文提供的是猜想与轶事,不是确定的数据。
- 「出到精算价值的五倍」来自作者在 1996 年一场会议上的见闻,精算价值的估算方法与来源论文没有披露,本课未能核对。
- 伯克希尔的条款细节(10 亿美元一层、50 亿美元起赔、1997 年 4 月 1 日生效、最坏情况 6 亿美元、账面价值 3%、市值 1.5%)已与 1996 年致股东信原文逐句核对一致。
- 「愿意在单一事件上亏 60 亿美元」是 Buffett 对自己承受能力的表述,不是对任何人的建议——能不能这样做取决于你的资本结构。
下一站:把公式、数字、对比和各站结论集中到一张表里,再用五道换了数字的题检查迁移。
13 / 速查与自测
速查表,以及五道换了数字的题
公式
| 项目 | 内容 | 出处 |
|---|---|---|
| Kelly 下注比例 | f* = W − (1−W)/R;零点在 W = 1/(1+R) | |
| 逆向选择下的出价(区间从 0 起算) | 成交概率 = b/上界;成交时净收益 = b × (a/2 − 1);期望 = 成交概率 × 净收益 | |
| 优势倍数对选择效应 (1) 式 | 回报 = a·m·[p·s + (1−p)],大于 1 则出价 | |
| 可选出价时的 (2) 式 | 收益 = a·m·[p·s(t) + (1−p)] − t;最优 t* 处为正就出 t* | |
| 百分比对称的平均 | 平均 = P × [(1+g) + 1/(1+g)] / 2 |
关键数字
| 项目 | 内容 | 出处 |
|---|---|---|
| 过度自信 | 理论上约 2% 落在 1%/99% 意外点之外,实际约 35% | |
| 回忆偏差 | 9/11 后 1–3 年,300 多名学生中 31% 说风险更低、26% 说与事发前相同 | |
| 抽奖 A / B | A:$2000 × 1% = $20;B:$1000 × 2.5% = $25 | |
| Kelly 的原文例子 | W = 60%、R = 1 → 0.6 − 0.4/1 = 0.2 | |
| Bazerman–Samuelson | 出价 60、区间 [0,100]、a = 1.5 → 成交时均值 30、对你 45、净 −15 | |
| 反例 | 区间 [1,2]、出价 2 → 必成交,期望价值 2.25,净 +0.25 | |
| 加州地震局那一层 | 10 亿美元,在累计损失 50 亿美元之上触发,保费为估计精算价值的五倍(a = 5,p 接近 0) | |
| 伯克希尔的自估上限 | 巨灾下税后最坏损失不超过 6 亿美元,不到账面价值的 3%、市值的 1.5% |
关键对比
| 项目 | 内容 | 出处 |
|---|---|---|
| 三级阶梯 | 风险=概率已知;不确定=概率未知;无知(UU)=状态未知 | |
| 两种不可知事件 | 晴天霹雳(突然、事后被合理化)vs 缓慢漂移(像给气球放气,事后不再像不可知);原文的漂移例子:纳斯达克四年涨五倍再大幅回落、苏联解体、艾滋病从全美累计 31 例死亡到全球流行 | |
| 两种收益来源 | 绝对优势(双方都得益)vs 信息不对称(零和) | |
| 两张格子的第二行 | E:你不知道、别人知道(危险水域);F:两边都不知道(低竞争)——都带事后诸葛亮风险 |
定性结论
| 项目 | 内容 | 出处 |
|---|---|---|
| 站 01 | 传统金融理论在概率未知处失效,决策论在状态未知处失效;到了无知这一级,需要的是互补能力与策略推断。 | |
| 站 01 | 判断一个情形属于哪一级,要看「状态清单能不能列出来」,不是看波动有多大。 | |
| 站 02 | 不可知不是可以回避的例外,而是常态;躲开它的人会在躲不掉的时候犯更大的错。 | |
| 站 02 | 如果没有一笔投资事后看起来蠢,说明你离不可知太远;怕被追责的人不适合这个领域。 | |
| 站 03 | 唯一性把套利者和怕被追责的人一起赶走,剩下的是稀薄的竞争和偏低的价格。 | |
| 站 03 | 值得期待超额回报的,是三个特征同时成立的机会,不是任何一个「看不懂」的机会。 | |
| 站 04 | UU 投资的超额回报付给的是与资本互补的稀缺能力,不是资本本身。 | |
| 站 04 | 没有互补能力时正确的动作是坐进有能力的人的挎斗,不是模仿他们。 | |
| 站 05 | UU 正是你经验最少、直觉最不可靠的地方,所以行为陷阱在这里最贵。 | |
| 站 05 | 别人的模糊厌恶是你的机会来源;你自己的模糊厌恶是你的成本。 | |
| 站 06 | 如果聪明且信息充分的人已经进场,那个领域的超额回报多半已经消失。 | |
| 站 06 | 投资优势应当和分散化同等重要地决定你投多少,而不是只决定投不投。 | |
| 站 07 | 对方愿意成交这件事本身就是信息;把它算进去,很多看着划算的出价其实是亏的。 | |
| 站 07 | 正确的教训不是「永远别交易」,而是「先看信息落差有多大」。 | |
| 站 08 | 先把绝对优势和信息不对称分开,再决定要不要把自己的优势讲给对方听。 | |
| 站 08 | 关键不是你知道多少,而是你相对于对方知道多少;先估自己的事后追责风险,再决定进不进。 | |
| 站 09 | 不要因为「对方可能更知情」就退出;把优势、知情概率、选择因子三件事同时摆出来再判断。 | |
| 站 09 | 你处在 UU 时,卖方不会被逼着全盘披露,他只会宣扬有利的那些维度。 | |
| 站 10 | 在规则本身都不确定的局里,「别人也不比我更知情」本身就是一项可交易的优势。 | |
| 站 11 | 在 UU 情形里,对方为劝退你所做的动作,本身就是关于价值的信息。 | |
| 站 11 | 说不准会涨会跌时,仍然可以把赔付放在资产值钱的那一侧。 | |
| 站 12 | 承认自己不知道,同时不假设别人知道——这两句必须一起用。 |
八条格言 A–H
站 00 说读完你能「复述八条格言,并各举一个原文里的例子」。查这张表之前,可以先合上它按编号自己说一遍,再逐条对照。英文是作者原句,下面一行是紧贴原句的中文。
| 格言 | 作者原句 | 依据 | 原文例子 | 出处 |
|---|---|---|---|---|
| 格言 A | Individuals with complementary skills enjoy great positive excess returns from UU investments. Make a sidecar investment alongside them when given the opportunity. 具备互补能力的人从 UU 投资中获得很高的正超额回报;有机会就在他们旁边做挎斗投资。 | UU 投资的超额回报付给的是与资本互补的稀缺能力,不是资本本身;没有这种能力的人只能与有能力的人同条件入场。 | 作者与 Tengion 的总裁合作过,因此能与有生物科技记录的风险投资机构以完全相同的条件投进去——一笔几乎所有人都被排除在外的投资。 | |
| 格言 B | The greater is your expected return on an investment, that is the larger is your advantage, the greater the percentage of your capital you should put at risk. 期望回报越高,也就是你的优势越大,投入风险的本金比例就应当越大。 | 多数投资建议假设市场有效、你没有优势;现实里机会有普通、有吸引、有非常吸引,显然该在更有吸引力的地方投得更多。 | 作者指出多数人并不执行:他们预期 30% 回报的那笔,拿到的钱只比预期 10% 的多一点点。 | |
| 格言 C | When information asymmetries may lead your counterpart to be concerned about trading with you, identify for her important areas where you have an absolute advantage from trading. You can also identify her absolute advantages, but she is more likely to know those already. 当信息不对称可能让对方担心与你交易时,向她指出你在哪些重要方面因交易而拥有绝对优势;她的绝对优势你也可以指出,但她多半已经知道。 | 纯粹的信息不对称会让双方推向无交易均衡;把「我为什么出这个价」解释成绝对优势,才能把交易从零和拉回双赢。 | 一块空地在 A 手里远不如在 B 手里值钱,A 卖给 B 两人都因绝对优势获益——但买方要当心卖方编造的绝对优势,比如集市上那句「今天收摊要给老婆拿钱」。 | |
| 格言 D | In a situation where probabilities may be hard for either side to assess, it may be sufficient to assess your knowledge relative to the party on the other side (perhaps the market). 在双方都可能难以评估概率的情形里,评估你相对于对方(也许就是市场)的知识,就可能已经够了。 | 你不可能拥有预见不可预见之事的神秘力量,但你可以估计自己相对于他人的理解程度;关键是判断别人是否觉得容易。 | Ricardo 大概不是军事专家,他只是明白买家会很少、而市场会过度贴现那份不可知的风险。 | |
| 格言 E | A significant absolute advantage offers some protection against potential selection. You should invest in a UU world if your advantage multiple is great, unless the probability is high the other side is informed and if, in addition, the expected selection factor is severe. 显著的绝对优势对潜在的选择效应提供一定保护。优势倍数大就应当在 UU 世界里投资,除非对方知情的概率很高,而且除此之外预期的选择因子还很严重。 | 把三件事放进同一个式子:回报 = a·m·[p·s + (1−p)],大于 1 就出价;两个「除非」是并列条件,必须同时成立才推翻结论。 | 加州地震局那一层:保费是估计精算价值的五倍(a = 5),而投保方掌握「大地震将至」内幕的可能性极低(p 接近 0)。 | |
| 格言 F | In UU situations, even sophisticated investors tend to underweight how strongly the value of assets varies. The goal should be to get good payoffs when the value of assets is high. 在 UU 情形里,连老练的投资者也倾向于低估资产价值的变动幅度。目标应当是:在资产价值高的时候拿到好赔付。 | UU 里连与赔付水平相关的事件都难预见,所以只能按收到的钱分饼;这时赔付结构放在哪一侧就成了唯一还能控制的东西。 | Ricardo 知道,威灵顿获胜、债券暴涨时他拿到的英镑,比战败、债券暴跌时他损失的英镑值钱得多;反面例子是风险投资的强制稀释融资,它恰恰在公司最不值钱时提高自己的份额。 | |
| 格言 G | Discounting for ambiguity is a natural tendency that should be overcome, just as should be overeating. 为模糊打折是一种应当克服的自然倾向,就像应当克服暴食一样。 | 模糊厌恶(Ellsberg)让人宁可赌标准硬币也不赌变形硬币;越模糊越厌恶,于是 UU 投资赶走了除最自主、最理性者之外的所有人。 | 加州地震局出到估计精算价值的五倍,纽约金融界仍然无人接单——那份折价就是模糊厌恶的价格表现。 | |
| 格言 H | Do not engage in the heuristic reasoning that just because you do not know the risk, others do. Think carefully, and assess whether they are likely to know more than you. When the odds are extremely favorable, sometimes it pays to gamble on the unknown, even though there is some chance that people on the other side may know more than you. 不要做「既然我不知道风险,别人一定知道」这种启发式推理。仔细想,评估他们是否可能比你知道得多。赔率极其有利时,即使对方有可能更知情,赌一把未知有时也是划算的。 | 多数投资者被吓退,是因为怕自己在「别人已知」那一格,哪怕认真评估会告诉他们那极不可能;先估计相对知识,再决定折不折价。 | 与多数保险不同,地震再保险的投保方几乎不可能掌握自身风险的内幕——所有人用的是同一个概率,Buffett 因此愿意独吃华尔街连一部分都不肯接的风险。 |
自测 1 · 补全过程
把 Bazerman–Samuelson 的设定换一组数:卖方的真实价值在 [0, 40] 上均匀分布,资产对你值她价值的 1.5 倍,你出价 24。请依次写出:① 成交概率;② 成交条件下她的平均价值;③ 这件东西对你值多少;④ 成交时你的净收益;⑤ 乘上成交概率后的期望;⑥ 一句话结论:出价换成 12 或 36 会不会改变结论的符号?
参考答案与回到哪一步
① 成交概率 = 24/40 = 60%。② 成交条件下她的平均价值 = (0 + 24)/2 = 12。③ 对你值 1.5 × 12 = 18。④ 成交时净 = 18 − 24 = −6。⑤ 期望 = 0.6 × (−6) = −3.6。⑥ 不会。区间从 0 起算时,成交时的净收益恒等于「出价 × (a/2 − 1)」,a = 1.5 时这个系数是 −0.25,所以出 12 亏 3、出 36 亏 9,符号永远是负的。要让符号翻过来,需要 a 大于 2。
常见的误读:最常见的错法是把「她的平均价值」当成 20(整个区间的中点),而不是「成交条件下」的 12。
自测 2 · 给定变化
把加州地震局那一层的条件改一处:保费从「估计精算价值的五倍」降到「一点二倍」,其他都不变(对方几乎不可能掌握内幕,作者写的是 p 接近 0)。用 (1) 式说明哪个参数动了、动了多少,Buffett 的判断会不会改变;再说一句:如果同时传出「加州刚更新了断层图、有一方看过而你没看过」,(1) 式里另外哪两个参数会动、往哪个方向动?
参考答案与回到哪一步
动的是优势倍数 a:从 5 降到 1.2。p 接近 0 时 (1) 式退化成 am,所以回报从大约 5m 掉到 1.2m。只要 m 接近 1(作者要求 m < 1),1.2m 仍然可能大于 1,但余地已经很薄——一点点费用、税或资金成本就能把它推到 1 以下。所以判断从「几乎不用犹豫」变成「要认真算」。断层图那条消息会同时推高 p(对方知情的概率不再接近 0)并压低 s(他知情时只会在对自己有利时成交,你成交到的平均更差);p 上升、s 下降会一起把 am[ps + (1−p)] 往下拉,这正是 Maxim E 里「除非…而且…」的两个条件同时出现的情形。
常见的误读:常见的错法是只改 p 而不动 a:保费变的是你的优势倍数,不是对方的知情概率。
自测 3 · 迁移到新例子
一个原文没有的情景:你熟识的一家区域物流公司老板要把一块城郊仓储用地卖给你。你手里有能把它长期租给电商仓配的渠道,这在当地没有第二个人有。他说他急着回笼资金。请用作者的三个特征(站 03)判断这笔投资是否属于「值得期待超额回报」的那一类,再用两张格子(站 08)说出你落在哪个方框;最后写出你在签字前必须确认的两件事,并说明它们各自对应 (1) 式里的哪个参数。
参考答案与回到哪一步
三个特征:① 底层是 UU——这块地未来的用途、当地规划、电商仓配的需求走向都不在可列举的状态清单上,成立;② 需要互补能力——你的渠道正是把地变值钱的东西,这笔交易不对一般市场开放,成立;③ 对手方不太可能更知情——这一条要打问号,他是本地人、是卖方,关于地块本身(产权、地质、规划风声)他几乎必然知道得更多。所以你不是在纯粹的方框 F,而是在「你有绝对优势、他有信息优势」的混合情形:格子的第二行,偏向 E(别人已知、你未知),但被你自己的绝对优势部分抵消。必须确认的两件事:第一,「急着回笼资金」是不是真的——如果真,那是他的绝对优势理由,对应 (1) 式里的 p(他并非因为知道坏消息才卖,p 下降);如果是编的,就落回 Maxim C 那段说的「卖方声称的绝对优势可能是假的」。第二,地块本身有没有你想不到的维度(抵押、道路改线、环保限制)——这决定 s,也就是他知情时你成交到的东西平均还剩多少价值。注意 s 必须单独赋一个值:它和 a、p 是三件独立的事,默认它等于 1 就等于假设「就算他更知情,也不会挑着卖给我」,那正是站 07 已经证明过的错误。顺带用 Maxim C:主动告诉他你的渠道,让他明白你的出价来自用途而不是内幕。
常见的误读:常见的错法是只看「我有渠道所以稳赚」,漏掉第三个特征——在这笔交易里它恰恰不成立。
自测 4 · 补全过程
一个机会:你估计获胜概率 W = 0.55,赢时所得与输时所失之比 R = 2。① Kelly 给出多大比例?② 把 W 降到 0.30,Kelly 给出什么?③ 这个符号翻转发生在哪个 W 上,公式怎么写?④ 用一句话说明:为什么这个零点并不包含在「优势越大投得越多」这句话里?
参考答案与回到哪一步
① f* = 0.55 − 0.45/2 = 0.55 − 0.225 = 0.325,即三成二五的本金。② f* = 0.30 − 0.70/2 = 0.30 − 0.35 = −0.05,负数,公式的意思是这个赌局对你不利,不要下注。③ 零点在 W = 1/(1+R),R = 2 时是 1/3 ≈ 33.3%。④ 因为 Maxim B 只描述「有优势时」比例随优势上升,它没有说优势从哪里开始;Kelly 把这条起跑线写了出来——W 在 1/(1+R) 以下时,再怎么调整比例都改善不了,正确的动作是不下注。
常见的误读:常见的错法是把 R = 2 的零点当成 50%;等额赌局(R = 1)的零点才是 50%。
自测 5 · 给定变化
一个原文没有的情景:一位你多年共事、判断力你信得过的投资人邀你按与他相同的条件投进一家早期公司。签字前你发现,他同时在募一只新基金,新基金投同一家公司的条款与你拿到的不一样。按 Maxim A(站 04)与 Maxim C(站 08),你该追问哪两件事?各自动摇的是挎斗投资成立的哪一个前提?
参考答案与回到哪一步
第一件:两套条款具体差在哪里,以及你这一套在坏结果下排在什么位置。Maxim A 的前提是「与他同条件入场」——挎斗的吸引力来自你和车手坐同一辆车;一旦清算顺序、反稀释或跟投权不同,你就不是在挎斗里,而是在他后面跑。第二件:他为什么把你放在这一套而不是那一套——也就是请他做 Maxim C 里那件事,说出他这样安排的绝对优势理由(比如新基金有承诺期限、监管或 LP 约束)。如果他给不出一个可验证的理由,那就落回作者的提醒:卖方声称的绝对优势可能是编的,而多数骗局之所以成立,是被骗者以为自己正在占便宜。这两件事动摇的是同一件事的两半:能力可信(车的性能)与利益一致(车手的诚信)。再用站 09 的三个参数收一次:条款不同并不改变你的优势倍数 a,它改变的是 s——在坏结果下你排在后面,意味着「万一他更知情、并且只在对自己有利时才让你进来」,你成交到的那一份平均还剩多少。迁移时最常见的漏洞就是默认 s = 1,也就是默认选择效应根本不存在。
常见的误读:常见的错法是只问「他还看好吗」,那检验的是他的判断,不是你和他条件是否一致。
复习与导出
复习清单里是你在词典里标记过的词。导出的 Markdown 笔记包含速查表四个分区、八条格言、各站结论、你当前的四组模型参数、先猜与自测记录,以及核查记录摘要。
导出按钮在页面顶栏。重置只清除本课程的参数、复习词、先猜与自测记录,不影响同一浏览器里的其他课程。
下一站:论文全文,41 页英文逐字,右侧有跟随滚动的目录。
14 / 原文全文
原文全文(英文)
[p. N] 是原刊页码。各站「对照原文」里的「在原文中查看」会跳到这里的对应段落并高亮;段末的「← 站 NN」回到引用它的那一步。右侧目录跟随滚动,底部的「返回上一位置」按跳转顺序逐级退回。原文全文(英文):以下是材料的完整原文,仅做分节与分段排版。点各站“对照原文”里的“在原文中查看”会跳到对应段落;段末的返回链接回到引用它的站。
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Capitalism and Society
Volume 1, Issue 2 · 2006 · Article 5
Investing in the Unknown and Unknowable
Richard Zeckhauser*
*Harvard University
Copyright © 2006 The Berkeley Electronic Press. All rights reserved.
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Abstract
From David Ricardo making a fortune buying British government bonds on the eve of the Battle of Waterloo to Warren Buffett selling insurance to the California earthquake authority, the wisest investors have earned extraordinary returns by investing in the unknown and the unknowable (UU). But they have done so on a reasoned, sensible basis. This essay explains some of the central principles that such investors employ. It starts by discussing “ignorance,” a widespread situation in the real world of investing, where even the possible states of the world are not known. Traditional finance theory does not apply in UU situations.
Strategic thinking, deducing what other investors might know or not, and assessing whether they might be deterred from investing, for example due to fiduciary requirements, frequently point the way to profitability. Most big investment payouts come when money is combined with complementary skills, such as knowing how to develop real estate or new technologies. Those who lack these skills can look for ”sidecar” investments that allow them to put their money alongside that of people they know to be both capable and honest. The reader is asked to consider a number of such investments.
Central concepts in decision analysis, game theory, and behavioral decision are deployed alongside real investment decisions to unearth successful investment strategies. These strategies are distilled into eight investment maxims. Learning to invest more wisely in a UU world may be the most promising way to significantly bolster your prosperity.
KEYWORDS: investing, unknown, unknowable, sidecar investment, fat-tailed distribution, Buffett, Kelly Criterion, asymmetric information
*I thank Miriam Avins, Paul Samuelson and Nils Wernerfelt for helpful comments.
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David Ricardo made a fortune buying bonds from the British government four days in advance of the Battle of Waterloo. He was not a military analyst, and even if he were, he had no basis to compute the odds of Napoleon’s defeat or victory, or hard-to-identify ambiguous outcomes. Thus, he was investing in the unknown and the unknowable. Still, he knew that competition was thin, that the seller was eager, and that his windfall pounds should Napoleon lose would be worth much more than the pounds he’d lose should Napoleon win. Ricardo knew a good bet when he saw it.¹
This essay discusses how to identify good investments when the level of uncertainty is well beyond that considered in traditional models of finance. Many of the investments considered here are one-time only, implying that past data will be a poor guide. In addition, the essay will highlight investments, such as real estate development, that require complementary skills. Most readers will not have such skills, but many will know others who do. When possible, it is often wise to make investments alongside them.
Though investments are the ultimate interest, the focus of the analysis is how to deal with the unknown and unknowable, hereafter abbreviated UU. Hence, I will sometimes discuss salient problems outside of finance, such as terrorist attacks, which are also unknown and unknowable.
This essay takes no derivatives, and runs no regressions.² In short, it eschews the normal tools of my profession. It represents a blend of insights derived from reading academic works and from trying to teach their insights to others, and from lessons learned from direct and at-a-distance experiences with a number of successful investors in the UU world. To reassure my academic audience, I use footnotes where possible, though many refer to accessible internet articles in preference to journals and books. Throughout this essay, you will find speculations and maxims, as seems called for by the topic. They will be labeled in sequence.
This informal approach seems appropriate given our present understanding of the topic. Initial beliefs about this topic are highly uncertain, or as statisticians would phrase it: “Prior distributions are diffuse.” Given that, the judicious use of illustrations, and prudent attempts to provide taxonomies and sort tea leaves, can substantially hone our beliefs, that is, tighten our future predictions.
1 The financing of 36 million pounds was floated on the London Stock Exchange. Ricardo took a substantial share. His frequent correspondent Thomas Malthus took 5,000 pounds on Ricardo’s recommendation, but sold out shortly before news of the Waterloo outcome was received. The evidence is clear that Ricardo, in his words, understood the “dismal forebodings” of the situation, including “its consequences, on our [England’s] finances.” See Sraffa (1952, Vol VI, pp. 202, 229 and surrounding material.
2 Ralph Gomory’s (1995) literary essay on the Unknown and Unknowable provided inspiration. Miriam Avins provided helpful comments.
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Part I of this essay talks about risk, uncertainty, and ignorance, the last carrying us beyond traditional discussions. Part II looks at behavioral economics, the tendency for humans to deviate in systematic ways from rational decision, particularly when probabilities are involved, as they always are with investments. Behavioral economics pervades the UU world. Part III addresses the role of skilled mathematical types now so prevalent in finance. It imparts a general lesson: If super-talented people will be your competitors in an investment arena, perhaps it is best not to invest. Its second half discusses a dispute between math types on money management, namely how much of your money to invest when you do have an edge. Part IV details when to invest when you can make more out of an investment, but there is a better informed person on the other side of the transaction. Part V tells a Buffett tale, and draws appropriate inferences. Part VI concludes.
I. RISK, UNCERTAINTY AND IGNORANCE
Escalating challenges to effective investing
The essence of effective investment is to select assets that will fare well when future states of the world become known. When the probabilities of future states of assets are known, as the efficient markets hypothesis posits, wise investing involves solving a sophisticated optimization problem. Of course, such probabilities are often unknown, banishing us from the world of the capital asset pricing model (CAPM), and thrusting us into the world of uncertainty.³
Were the financial world predominantly one of mere uncertainty, the greatest financial successes would come to those individuals best able to assess probabilities. That skill, often claimed as the domain of Bayesian decision theory, would swamp sophisticated optimization as the promoter of substantial returns.
The real world of investing often ratchets the level of non-knowledge into still another dimension, where even the identity and nature of possible future states are not known. This is the world of ignorance. In it, there is no way that one can sensibly assign probabilities to the unknown states of the world. Just as traditional finance theory hits the wall when it encounters uncertainty, modern decision theory hits the wall when addressing the world of ignorance. I shall employ the acronym UU to refer to situations where both the identity of possible future states of the world as well as their probabilities are unknown and unknowable. Table 1 outlines the three escalating categories; entries are explained throughout the paper.
3 The classic description of uncertainty, a situation where probabilities could not be known, is due to Frank Knight (1921).
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Table 1. Escalating Challenges to Effective Investing
| | Knowledge of States of the World | Investment Environment | Skills Needed | |---|---|---|---| | Risk | Probabilities known | Distributions of returns known | Portfolio optimization | | Uncertainty U | Probabilities unknown | Distributions of returns conjectured | Portfolio optimization, Decision theory | | Ignorance UU | States of the world unknown | Distributions of returns conjectured, often from deductions about other’s behavior. Complementary skills often rewarded along side investment | Portfolio optimization. Decision theory. Complementary skills (ideal) Strategic inference. |
This essay has both dreary and positive conclusions about investing in a UU world. The first dreary conclusion is that unknowable situations are widespread and inevitable. Consider the consequences for financial markets of global warming, future terrorist activities, or the most promising future technologies. These outcomes are as unknowable today as were the 1997 Asian meltdown, the 9/11 attacks, or the NASDAQ soar and swoon at the end of the century, shortly before they were experienced.
These were all aggregate unknowables, affecting a broad swath of investors. But many unknowables are idiosyncratic or personal, affecting only individuals or handfuls of people, such as: If I build a 300-home community ten miles to the west of the city, will they come? Will the Vietnamese government let me sell my insurance product on a widespread basis? Will my friend’s new software program capture the public fancy, or if not might it succeed in a completely different application? Such idiosyncratic UU situations, I argue below, present the greatest potential for significant excess investment returns.
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The second dreary conclusion is that most investors – whose training, if any, fits a world where states and probabilities are assumed known – have little idea of how to deal with the unknowable. When they recognize its presence, they tend to steer clear, often to protect themselves from sniping by others. But for all but the simplest investments, entanglement is inevitable – and when investors do get entangled they tend to make significant errors.
The first positive conclusion is that unknowable situations have been and will be associated with remarkably powerful investment returns. The second positive conclusion is that there are systematic ways to think about unknowable situations. If these ways are followed, they can provide a path to extraordinary expected investment returns. To be sure, some substantial losses are inevitable, and some will be blameworthy after the fact. But the net expected results, even after allowing for risk aversion, will be strongly positive.
Do not read on, however, if blame aversion is a prime concern: The world of UU is not for you. Consider this analogy. If in an unknowable world none of your bridges fall down, you are building them too strong. Similarly, if in an unknowable world none of your investment looks foolish after the fact, you are staying too far away from the unknowable.
Warren Buffett, a master at investing in the unknowable, and therefore a featured player in this essay, is fond of saying that playing contract bridge is the best training for business. Bridge requires a continual effort to assess probabilities in at best marginally knowable situations, and players need to make hundreds of decisions in a single session, often balancing expected gains and losses. But players must also continually make peace with good decisions that lead to bad outcomes, both one’s own decisions and those of a partner. Just this peacemaking skill is required if one is to invest wisely in an unknowable world.
The nature of unknowable events
Many of the events that we classify as unknowable arrive in an unanticipated thunderclap, giving us little or no time to anticipate or prepare. But once they happen, they do not appear that strange. The human mind has an incredible ability to find a rationalization for why it should have been able to conjecture the terror attack of 9/11; or the Asian tsunamis of 1997 and 2005, respectively caused by currency collapse and underwater earthquake. This propensity to incorporate hindsight into our memories – and to do so particularly when Monday morning quarterbacks may attack us – hinders our ability to anticipate extreme events in the future. We learn insufficiently from our misestimates and mistaken decisions.
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Other unknowable events occur over a period of time, as did the collapse of the Soviet Union. Consider most stock market swings. Starting in January 1996, the NASDAQ rose five-fold in four years. Then it reversed field and fell by two thirds in three years. Such developments are hardly thunderclaps. They are more like blowing up a balloon and then dribbling out the air. In retrospect, these remarkable swings have lost the flavor of an unknowable event, even though financial markets are not supposed to work that way. If securities prices at any moment incorporate all relevant information, a property that is usually posited, long-term movements in one direction are hardly possible, since strong runs of unanticipated good news or bad news will be exceedingly rare. Similarly, the AIDS scourge now seems familiar territory, though 25 years ago – when there had been only 31 cumulative deaths in the U.S. from AIDS – no one would have predicted a world-wide epidemic killing tens of millions and vastly disrupting the economies of many poor nations.
Are UU events to be feared? Warren Buffett (1996) once remarked: “It is essential to remember that virtually all surprises are unpleasant.” Most salient UU events seem to fall into the left tail of unfortunate occurrences. This may be more a matter of perception than reality. Often an upside unknowable event, say the diminution of terror attacks or recovery from a dread disease, is difficult to recognize. An attack on any single day was not likely anyway, and the patient still feels lousy on the road to recovery. Thus, the news just dribbles in, as in a financial market upswing. B.F. Skinner, the great behavioral psychologist, taught us that behavior conditioned by variable interval reinforcement – engage in the behavior and from time-to-time the system will be primed to give you a payoff – was the most difficult to extinguish. Subjects could never be sure that another reward would not be forthcoming. Similarly, it is hard to discern when a string of inconsistently spaced episodic events has concluded. If the events are unpleasant, it is not clear when to celebrate their end.
Let us focus for the moment on thunderclap events. They would not get this title unless they involved something out of the ordinary, either good or bad. Casual empiricism – judged by looking at local, national and international headlines – suggests that thunderclap events are disproportionately adverse. Unlike in the old television show, The Millionaire, people do not knock on your door to give you a boatload of money, and in Iraq terror attacks outnumber terrorist arrests manifold.
The financial arena may be one place with an apparently good ratio of upside to downside UU events, particularly if we include events that are drifts and not thunderclaps. By the end of 2004, there were 2.5 million millionaires in the United States, excluding housingwealth. http://money.cnn.com/2005/06/09/news/world_wealth/ Many of these individuals, no doubt, experienced upside UU events. Some events, such as the sustained boom in housing prices, were experienced by many, but many upside events probably only affected the individual and perhaps a few others; such events include an unexpected lucrative job, or having a business concept take a surprisingly prosperous turn, or having a low-value real estate holding explode in value, etc.
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We hear about the lottery winner -- the big pot, the thunderclap, and the gain for one individual makes it newsworthy. In contrast, the tens of thousands of UU events that created thousands of new real estate millionaires are mostly reported in dry aggregate statistics. Moreover, contrary to the ads in the back of magazines, there is usually not a good way to follow these “lucky folks,” since some complementary skill or knowledge is likely to be required, not merely money and a wise choice of an investment. Thus, many favorable UU financial events are likely to go unchronicled.
While still in this Pollyannish frame, it is worth noting the miracles of percentage symmetry given extreme events. Posit that financial prices move in some symmetric fashion. Given that negative prices are not possible, such changes must be in percentage rather than absolute terms.⁴ We will not notice any difference between percentage and absolute if changes are small relative to the mean. Thus, if a price of 100 goes up or down by an average of 3 each year, or up by a ratio of 103/100 or down by 100/103 hardly matters. But change that 3 to a 50, and the percentage symmetry helps a great deal. The price becomes 100(150/100) or 100(100/150)), which has an average of 117. If prices are anything close to percentage symmetric, as many believe they are, then big swings are both enemy and friend: enemy because they impose big risks, friend because they offer substantial positive expected value.
Many millionaires have made investments that multiplied their money 10-fold, and some 100-fold. The symmetric geometric model would expect events that cut one’s stake to 1/10th or 1/100th of its initial value to be equally likely. The opportunity to get a 10 or 100 multiple on your investment as often as you lose virtually all of it is tremendously attractive.
There is, of course, no reason why investments must yield symmetric geometric returns. But it would be surprising not to see significant expected excess returns to investments that have three characteristics addressed in this essay: (1) UU underlying features, (2) complementary capabilities are required to
4 This is sometimes expressed that things move geometrically rather than arithmetically, or that the logarithm of price has a traditional symmetric distribution. The most studied special case is the lognormal distribution. See “Life is log-normal” by E. Limpert and W. Stahel, http://www.inf.ethz.ch/personal/gut/lognormal/brochure.html, for an argument on the widespread applicability of this distribution.
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undertake them, so the investments are not available to the general market, and (3) it is unlikely that a party on the other side of the transaction is better informed. That is, UU may well work for you, if you can identify general characteristics of when such investments are desirable, and when not.
These very attractive three-pronged investments will not come along everyday. And when they do, they are unlikely to scale up as much as the investor would like, unlike an investment in an underpriced NYSE stock, which scales nicely, at least over the range for most individual investors. Thus, the UU-sensitive investor should be constantly on the lookout for new opportunities. That is why Warren Buffett trolls for new businesses to buy in each Berkshire-Hathaway annual report, and why most wealthy private investors are constantly looking for new instruments or new deals.
Uniqueness
Many UU situations deserve a third U, for unique. If they do, arbitrageurs – who like to have considerable past experience to guide them – will steer clear. So too will anybody who would be severely penalized for a poor decision after the fact. An absence of competition from sophisticated and well-monied others spells the opportunity to buy underpriced securities.
Most great investors, from David Ricardo to Warren Buffett, have made most of their fortunes by betting on UUU situations. Ricardo allegedly made 1 million pounds (over $50 million today) – roughly half of his fortune at death – on his Waterloo bonds.⁵ Buffett has made dozens of equivalent investments. Though he is best known for the Nebraska Furniture Mart and See’s Candies, or for long-term investments in companies like the Washington Post and Coca Cola, insurance has been Berkshire Hathaway’s firehose of wealth over the years. And insurance often requires UUU thinking. A whole section below discusses Buffett’s success with what many experts saw as a UUU insurance situation, so they steered clear; but he saw it as offering excess premium relative to risk, so he took it all.
Speculation 1: UUU investments – unknown, unknowable and unique – drive off speculators, which creates the potential for an attractive low price.
Some UU situations that appear to be unique are not, and thus fall into categories that lend themselves to traditional speculation. Corporate takeover bids are such situations. When one company makes a bid for another, it is often
5 Ricardo’s major competitors were the Baring Brothers and the Rothschilds. Do not feel sorry for the Rothschilds. In the 14 years from 1814 to 1828 they multiplied their money 8-fold, often betting on UU situations, while the Baring Brothers lost capital. http://www.businessweek.com/1998/49/b3607071.htm. Analysis based on Niall Ferguson’s House of Rothschild.
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impossible to determine what is going on or what will happen, suggesting uniqueness. But since dozens of such situations have been seen over the years, speculators are willing to take positions in them. From the standpoint of investment, uniqueness is lost, just as the uniqueness of each child matters not to those who manufacture sneakers.
Weird Causes and Fat Tails
The returns to UUU investments can be extreme. We are all familiar with the Bell Curve (or Normal Distribution), which nicely describes the number of flips of a fair coin that will come up heads in a large number of trials. But such a mechanical and controlled problem is extremely rare. Heights are frequently described as falling on a Bell Curve. But in fact there are many too many people who are extremely tall or extremely short, due say to glandular disturbances or genetic abnormalities. The standard model often does not apply to observations in the tails. So too with most disturbances to investments. Whatever the explanation for the October 1987 crash, it was not due to the usual factors that are used to explain market movements.⁶
More generally, movements in financial markets and of investments in general appear to have much thicker tails than would be predicted by Brownian motion, the instantaneous source of Bell Curve outcomes. That may be because the fundamental underlying factors produce thicker tails, or because there are rarely occurring anomalous or weird causes that produce extreme results, or both. The UU and UUU models would give great credence to the latter explanation, though both could apply.⁷
Complementary skills and UU investments
A great percentage of UU investments, and a greater percentage of those that are UUU, provide great returns to a complementary skill. For example, many of America’s great fortunes in recent years have come from real estate. These returns came to people who knew where to build, and what and how. Real estate developers earn vast amounts on their
6 Hart and Tauman (2004) show that market crashes are possible purely due to information processing among market participants, with no new information. They observe that the 1987 crash – 20% in a day – happened despite no new important information becoming available, nor negative economic performance after the crash. Market plunges due to ordinary information processing defies any conventional explanation, and is surely a UU event.
7 Nassim Taleb and Benoit Mandelbrot posit that many financial phenomena are distributed according to a power law, implying that the relative likelihood of movements of different sizes depends only on their ratio. Thus, a 20% market drop relative to a 10% drop is the same as a 10% drop relative to a 5% drop. http://www.fooledbyrandomness.com/fortune.pdf. Power distributions have fat tails. In their empirical studies, economists frequently assume that deviations from predicted values have normal distributions. That makes computations tractable, but evidence suggests that tails are often much thicker than with the normal. Zeckhauser and Thompson (1970).
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capital because they have complementary skills. Venture capitalists can secure extraordinary returns on their own monies, and charge impressive fees to their investors, because early stage companies need their skills and their connections. In short, the return to these investments comes from the combination of scarce skills and wise selection of companies for investment. High tech pioneers – Bill Gates is an extreme example – get even better multiples on their investment dollars as a complement to their vision and scientific insight.⁸
Alas, few of us possess the skills to be a real estate developer, venture capitalist or high tech pioneer. But how about becoming a star of ordinary stock investment? For such efforts an ideal complementary skill is unusual judgment. Those who can sensibly determine when to plunge into and when to refrain from UUU investments gain a substantial edge, since mispricing is likely to be severe. Bill Miller, the famed manager of the Legg Mason Value Fund, had a unique record of beating the S&P; his string through December 2005 was 15 years in a row. In October 2004 he spoke at Harvard University, and explained in detail why he made major purchases of Google at its public offering, surely a UUU situation given the nature of the company and the fact that it was offered through a Dutch auction.⁹ Virtually all in the audience were impressed that he made this decision -- the stock came out at $85 in August that year and had run up to $140. But Miller recognized that explaining past successes is not a challenge. He went on to proclaim Google a great investment for the future. How right he was. Google was selling at $380 in September 2006, when this essay was completed. Alas, 2006 was not kind to Miller. By September, his Value Fund was 12% behind the S&P for the year. Only time will tell whether Miller has lost his touch or is merely in a slump.
Warren Buffett’s unusual judgment operates with more prosaic companies, such as oil producers and soft drink firms. He is simply a genius at everyday tasks, such as judging management capability or forecasting company progress. He drains much of the unknowable in judging a company’s future. But he has other advantages. A number of Buffett’s investments have come to him because companies sought him out, asking him to make an investment and also to serve on their board, valuing his discretion, his savvy, and his reputation for rectitude – that is, his complementary skills, not merely his money. And when he is called on for such reasons, he often gets a discounted price. Those like Miller
8 Complementary skills can also help the less affluent invest. Miriam Avins, a good friend, moved into an edgy neighborhood in Baltimore because the abandoned house next door looked like a potential community garden, she knew she had the skills to move the project forward, and she valued the learning experience the house would bring to her family. Her house value doubled in 3 years, and her family learned as well.
9 Dinner speech to annual executive program on Investment Decisions and Behavioral Finance, John F. Kennedy School of Government, Harvard University, October 14, 2004.
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and Buffet, who can leverage complementary skills in stock market investment, will be in a privileged position of limited competition. But that will accomplish little if they do not show courage and make big purchases where they expect high payoffs. But the lesson for regular mortals is not to imitate Warren Buffett or Bill Miller; that makes no more sense than trying to play tennis like Roger Federer. Each of them has an inimitable skill. If you lack Buffett-Miller capabilities, you will get chewed up as a bold stock picker.
Note, by the way, the generosity with which great investors with complementary skills explain their successes – Buffett in his annual reports, Miller at Harvard, and any number of venture capitalists who come to lecture to MBAs. These master investors need not worry about the competition, since few others possess the complementary skills for their types of investments. Few UU investment successes come from catching a secret, such as the whispered hint of “plastics” in the movie The Graduate. Mayer Amschel Rothschild had five sons who were bright, disciplined, loyal and willing to disperse. These were the complementary skills. The terrific investments in a UU world – and the Rothschild fortune – followed.
Before presenting a maxim about complementary skills, I present you with a decision problem. You have been asked to join the Business Advisory Board of a company named Tengion. Tengion was founded in 2003 to develop and commercialize a medical breakthrough: “developing new human tissues and organs (neo-tissues and neo-organs) that are derived from a patient’s own cells…[this technology] harnesses the body’s ability to regenerate, and it has the potential to allow adults and children with organ failure to have functioning organs built from their own (autologous) tissues.” http://www.tengion.com/
This is assuredly a UU situation, doubly so for you, since until now you had never heard the term neo-organ. A principal advantage of joining is that you would be able to invest a reasonable sum on the same basis as the firm’s insiders and venture capitalists. Would you choose to do so?
I faced this decision problem because I had worked successfully with Tengion’s president on another company many years earlier. I was delighted with the UU flavor of the situation, and chose to join and invest because I would be doing so on the same terms as sophisticated venture capital (VC) firms with track records and expertise in relevant biotech areas. This was an investment from which virtually everyone else would be excluded. In addition, it would benefit from the complementary skills of the VCs.
Sidecar investments
Such undertakings are “sidecar investments”; the investor rides along in a sidecar pulled by a powerful motorcycle. The more the investor is distinctively positioned to have confidence in the driver’s integrity and his motorcycle’s capabilities, the more attractive the investment, since its price will be lower due to limited competition. Perhaps the premier sidecar investment ever available to the ordinary investor was Berkshire Hathaway, many decades back. One could have invested alongside Warren Buffett, and had him take a ridiculously low compensation for his services. (In recent years, he has been paid $100,000, with no bonus or options.) But in 1960 who had heard of Warren Buffett, or knew that he would be such a spectacular and poorly compensated investor? Someone who knew Buffett and recognized his remarkable capabilities back then was in a privileged UU situation.
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Maxim A: Individuals with complementary skills enjoy great positive excess returns from UU investments. Make a sidecar investment alongside them when given the opportunity.
Do you have the courage to apply this maxim? It is January 2006 and you, a Western investor, are deciding whether to invest in Gazprom, the predominantly government-owned Russian natural gas giant in January 2006. Russia is attempting to attract institutional investment from the West; the stock is sold as an ADR, and is soon to be listed on the OTC exchange; the company is fiercely profitable, and it is selling gas at a small fraction of the world price. On the upside, it is generally known that large numbers of the Russian elite are investors, and here and there it is raising its price dramatically. On the downside, Gazprom is being employed as an instrument of Russian government policy, e.g., gas is sold at a highly subsidized price to Belarus, because of its sympathetic government, yet the Ukraine is being threatened with more than a four-fold increase in price, in part because its government is hostile to Moscow. And the company is bloated and terribly managed. Finally, experiences, such as those with Yukos Oil, make it clear that the government is powerful, erratic, and ruthless.
This is clearly a situation of ignorance, or UU. The future states of the world are simply not known. Will the current government stay in power? Will it make Gazprom its flagship for garnering Western investment? If so, will it streamline its operations? Is it using foreign policy concerns as a device mainly to raise prices, a strong positive, and is it on a path to raise prices across the board? Will it complete its proposed pipelines to Europe? What questions haven’t you thought of, whose answers could dramatically affect your payout? Of course, you should also determine whether Western investors have distinct disadvantages as Gazprom shareholders, such as unique taxes, secondary voting status, etc. Finally, if you determine the investment is favorable given present circumstances, you should ask how quickly Russia could change conditions against outsiders, and whether you will be alert and get out if change begins.
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You could never learn about the unknowables sufficiently well to do traditional due diligence on a Gazprom investment. The principal arguments for going ahead would be that Speculation 1 and Maxim A apply. If you could comfortably determine that the Russian elite was investing on its own volition, and that foreigners would not be discriminated against, or at least not quickly, this would make a sensible sidecar investment.¹⁰
II. BEHAVIORAL ECONOMICS AND DECISION TRAPS
Behavioral decision has shaken the fields of economics and finance in recent decades. Basically, this work shows in area after area that individuals systematically deviate from making decisions in a manner that would be admired by Jimmie Savage (1954) and Howard Raiffa (1968), pioneers of the rational decision paradigm. As one illustration, such deviators could be turned into money pumps: They would pay to pick gamble B over gamble A. Then with A reframed as A’, but not changed in its fundamentals, they would pay to pick A over B.
That is hardly the path to prudent investment, but alas behavioral decision has strong descriptive validity. Behavioral decision has important implications for investing in UU situations. When considering our own behavior, we must be extremely careful not to fall prey to the biases and decision traps it chronicles. Almost by definition, UU situations are those where our experience is likely to be limited, where we will not encounter situations similar to other situations that have helped us hone our intuition.
Virtually all of us fall into important decision traps when dealing with the unknowable. This section discusses two, overconfidence and recollection bias, and then gives major attention to a third, misweighting differences in probabilities and payoffs. But there are dozens of decision traps, and some will appear later in this essay. The Nobel Prize winning work of Daniel Kahneman and Amos Tversky (the latter was warmly cited, but died too soon to win),¹¹ and the delightful and insightful Poor Charlie’s Almanack, written by Charles Munger (Warren Buffett’s partner) respectively provide academic and finance-oriented discussions of such traps.
There are at least three major objections to behavioral economics: First, in competitive markets, the anomalies it describes will be arbitraged away. Second, the anomalies only appear in carefully crafted situations; they are much like optical illusions, intriguing but rarely affecting everyday vision. Third, they describe the way people do behave, but not the way they should behave. The first
10 This investment was proposed when this paper was presented at a conference sponsored by the Wharton School on January 6, 2006. The price was then 33.60. At press time nine months later it was $47.
11 See http://nobelprize.org/nobel_prizes/economics/laureates/2002/public.html.
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objection is tangential to this discussion; competitive markets and arbitrage are not present in many UU situations, and in particular not the ones that interest us. The second objection is relatively unimportant because, in essence, UU situations are those where optical illusions rule the world. A UU world is not unlike a Fun House. Objection three I take up seriously below; this essay is designed to help people behave more rationally when they invest.
Let us first look at the biases.
Overconfidence
When individuals are assessing quantities about which they know very little, they are much too confident of their knowledge (Alpert and Raiffa, 1982). Appendix A offers you a chance to test your capabilities in this regard. For each of eight unknown quantities, such as the area of Finland, you are asked to provide your median estimate, then your 25th and 75th percentile estimates (i.e., it is one quarter likely the true value will be more extreme than either of the two), and then your 1st and 99th percentiles, what are referred to as surprise points. In theory, an individual should have estimates outside her surprise points about 2% of the time. In fact, even if warned about overconfidence, individuals are surprised about 35% of the time.¹² Quite simply, individuals think they know much more about unknowable quantities than they do.
Speculation 2: Individuals who are overconfident of their knowledge will fall prey to poor investments in the UU world. Indeed, they are the green plants in the elaborate ecosystem of finance where there are few lions, like Bill Miller and Warren Buffett; many gazelles, like you and me; and vast acres of grass ultimately nourishing us all.
Recollection bias
A first lesson in dealing with UU situations is to know thyself. One good way to do this is to review successes and failures in past decisions. However, since people do not have a long track record, they naturally turn to hypotheticals from the past: Would I have judged the event that actually occurred to be likely? Would I have made that good investment and steered clear of the other bad one? Would I have sold out of NASDAQ stocks near New Year 2001? Alas, human beings do not do well with such questions. They are subject to substantial recollection bias.¹³
Judging by articles in the New York Times leading up to 9/11/2001, there was virtually no anticipation of a major terrorist attack on the United States; it
12 Approximate average from Investment Decisions and Behavioral Finance, executive program, annually fall 2001-2006, and API-302, Analytic Frameworks for Policy course. The former is chaired, the latter taught by Richard Zeckhauser, Kennedy School, Harvard University.
13 See Gilbert (2006) for insightful discussions of the problems of rationalization and corrigibility.
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was a clear UUU event. But that is not what respondents told us one to three years later. They were asked to compare their present assessments of the likelihood of a massive terrorist attack with what they estimated that likelihood to be on September 1, 2001. Of more than 300 Harvard Law and Kennedy School students surveyed, 31% rated the risk as now lower, and 26% rated the risk as the same as they had perceived the 9/11 risk before the event.¹⁴ We can hardly be confident that investors will be capable of judging how they would have assessed UU risks that occurred in the past.
Misweighting probabilities and preferences
The two critical components of decision problems are payoffs and probabilities. Effective decision requires that both be carefully calibrated. Not surprisingly, Prospect Theory, the most important single contribution to behavioral decision theory to date, finds that individuals’ responses to payoffs and probabilities are far from rational.¹⁵ To my knowledge, there is no tally of which contributes more to the loss of expected utility from the rational norm. (Some strong supporters of behavioral decision theory, however, think it is our norms that are misguided, and that the way the brain naturally perceives outcomes, not the prescriptions of decision theorists and economists, should be the guideline.)
Whether drawing from Prospect Theory or observation, it seems clear that individuals draw insufficient distinctions among small probabilities. Consider the following experiment, in which an individual is asked to pick A or B.
Lottery Choice: Payoffs Versus Probabilities
| | Payoff | Probability | |---|---|---| | A | $2000 | 0.01 | | B | $1000 | 0.025 |
A rational, risk averse individual should opt for B, since it offers a higher expected value – $25 versus $20 – and less risk. Yet past experiments have shown that many individuals choose A, since in accordance with Prospect Theory they do not distinguish sufficiently between two low probability events. We speculate further that if we used named contingencies – for example, the Astros or the Blue Jays win the World Series – alongside their probabilities, the frequency of preference for A would increase. The contingencies would be selected, of course, so that their likelihood of occurrence, as indicated by odds in Las Vegas, would match those in the example above.
14 See Viscusi and Zeckhauser (2005).
15Kahneman and Tversky (1979).
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This hypothetical experiment establishes a baseline for another one that involves UU events. This time the prizes are based on events that are as close to the spectrum of UU events as possible, subject to the limitation that they must be named.¹⁶ Thus, a contingency might be that a 10,000-ton asteroid passed within 50,000 miles of Earth within the past decade, or that more than a million mammals crossed the border from Tanzania to Kenya last year. To begin our experiment, we ask a random sample of people to guess the likelihood of these contingencies. We then alter the asteroid distance or the number of animals in the question until the median answer is 0.03. Thus, if 50,000 miles got a median answer of 0.05, we would adjust to 40,000 miles, etc.
We now ask a new group of individuals to choose between C and D, assuming that we have calibrated the asteroid and mammal question to get to 0.03.
Lottery Choice: Payoffs Versus Probability or UU Event
| | Payoff | Required contingency | |---|---|---| | C | $2000 | Draw a 17 from an urn with balls numbered 1 to 100 | | D | $1000 | 10,000-ton asteroid passed within 40,000 miles of Earth |
Lotteries C and D should yield their prizes with estimated probabilities of 1% and 3% respectively. Still, we suspect that many more people would pick C over D than picked A over B, and that this would be true for the animal movement contingency as well.¹⁷
A more elaborated version of this problem would offer prizes based on alternative UU contingencies coming to pass. For example, we might recalibrate the mammal-crossing problem to get a median response of 0.01. We would then have:
16 This illustration employs events that may have happened in the past, but subjects would not know. The purpose is to make payoffs immediate, since future payoffs suffer from a different form of bias.
17 The experiment is at a disadvantage in getting this result, since peoples’ assessments of the contingencies’ probabilities would vary widely. Some would pick D because they attached an unusually high probability to it. In theory, one could ask people their probability estimate after they made their choice, and then look only at the answers of those for whom the probability was in a narrow range. However, individuals would no doubt adjust their retrospective probability estimates to help rationalize their choice.
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Lottery Choice: Payoffs Versus UU Events
| | Payoff | Required contingency | |---|---|---| | E | $2000 | Calibrated large number of animals crossed the Tanzania-Kenya border | | F | $1000 | 10,000 ton-asteroid passed within 40,000 miles of Earth |
Here the values have been scaled so the median response is three times higher for the asteroid event than the animal crossing. We would conjecture again that E would be chosen frequently.¹⁸ People do not like to rely on the occurrence of UU events, and choices based on distinguishing among their probabilities would be an unnatural act.
Daniel Ellsberg (1961) alerted us to ambiguity aversion long before he created a UU event by publishing the Pentagon papers. In an actual experiment, he showed, in effect, that individuals preferred to win a prize if a standard coin flip came up heads, rather than to win that prize by choosing either heads or tails on the flip of a mangled coin whose outcome was difficult to predict.¹⁹ Such ambiguity aversion may be a plausible heuristic response to general decisions under uncertainty, since so often there is a better-informed person on the other side – such as someone selling a difficult-to-assess asset.²⁰ Whatever the explanation, ambiguity aversion has the potential to exert a powerful effect. Extending Ellsberg one step further, it would seem that the more ambiguous the contingencies, the greater the aversion. If so, UU investments will drive away all but the most self-directed and rational thinking investors. Thus, Speculation 1 is reinforced.
18 This experiment and the choice between lotteries C and D above only approximate those with numerical probabilities, since they are calibrated for median responses and individuals’ estimates will differ.
19 In fact, Ellsberg’s experiment involved drawing a marble of a particular color from an urn. Subjects preferred a situation where the percentage of winning marbles was known, even if they could bet on either side when it was unknown.
20 Fox and Tversky (1995, p. 585) found that ambiguity aversion was “produced by a comparison with less ambiguous events or with more knowledgeable people….[it] seems to disappear in a noncomparative context.” Ambiguity aversion is still relevant for investments, if alternative investments are available and contemplated.
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III. MATH WHIZZES IN FINANCE AND CASH MANAGEMENT
The major fortunes in finance, I would speculate, have been made by people who are effective in dealing with the unknown and unknowable. This will probably be truer still in the future. Given the influx of educated professionals into finance, those who make their living speculating and trading in traditional markets are increasingly up against others who are tremendously bright and tremendously well-informed.²¹
By contrast, those who undertake prudent speculations in the unknown will be amply rewarded. Such speculations may include ventures into uncharted areas, where the finance professionals have yet to run their regressions, or may take completely new paths into already well-traveled regions.²² It used to be said that if your shoeshine boy gave you stock tips it was time to get out of the market. With shoeshine boys virtually gone and finance Ph.D.’s plentiful, the new wisdom might be:
When your math whiz finance Ph.D. tells you that he and his peers have been hired to work in the XYZ field, the spectacular returns in XYZ field have probably vanished forever.
Similarly, the more difficult a field is to investigate, the greater will be the unknown and unknowables associated with it, and the greater the expected profits to those who deal sensibly with them. Unknownables can’t be transmuted into sensible guesses -- but one can take one’s positions and array one’s claims so that unknowns and unknowables are mostly allies, not nemeses. And one can train to avoid one’s own behavioral decision tendencies, and to capitalize on those of others.
Assume that an investor is willing to invest where he has an edge in UU situations. How much capital should then be placed into each opportunity? This
21 Paul Samuelson, who attends closely to most aspects of the finance field, attests to this challenge. He observed that the Renaissance Group, run by former Stony Brook math professor Jim Simons, is “perhaps the only long-time phenomenal performer [in traditional financial markets] on a risk-corrected basis.” Private communication, June 15, 2006.
22I saw such path blazing by my former business partner Victor Niederhoffer in the 1970s, when he ventured into commodity investing. His associates hand recorded commodity prices at 15-minute intervals. He lined up a flotilla of TRS-80 Radio Shack computers to parallel process this information. His innovative data mining, spurred by accompanying theories of how markets behave, gave him a giant advantage over major investment houses. Niederhoffer continues along unusual paths, now making a second fortune after losing his first in the collapse of the Thai baht in 1997. http://www.greenwichtime.com/business/scn-sa-black1jun18,0,3887361.story?page=5&coll=green-business-headlines
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problem is far from the usual portfolio problem. It is afflicted with ignorance, and decisions must be made in sequential fashion. Math whizzes have discussed this problem in a literature little known to economists, but frequently discussed among gamblers and mathematicians. The most famous contribution is an article published 50 years ago by J.L. Kelly, an AT&T scientist. His basic formula, which is closely related to Claude Shannon’s information theory, tells you how much to bet on each gamble as a function of your bankroll, with the probability of winning and the odds as the two parameters. Perhaps surprisingly, the array of future investment opportunities does not matter.
Kelly’s Criterion, as it is called, is to invest an amount equal to W – (1-W)/R, where W is your probability of winning, and R is the ratio of the amount you win when you win to the amount you lose when you lose. Thus, if you were 60% likely to win an even money bet, you would invest .6 – (1-.6)/1 = .2 or 20% of your capital.
It can be shown that given sufficient time, the value given by any other investment strategy will eventually be overtaken in value by following the Kelly Criterion, which maximizes the geometric growth rate of the portfolio. That might seem to be definitive. But even in the mathematical realm of optimal dynamic investment strategies, assuming that all odds and probabilities are known, we encounter a UU situation.
Paul Samuelson, writing in a playful mood, produced an article attacking the Kelly Criterion as a guide for practice. His article uses solely one-syllable words. His abstract observes: “He who acts in N plays to make his mean log of wealth as big as it can be made will, with odds that go to one as N soars, beat me who acts to meet my own tastes for risk.”²³ Samuelson correctly prescribes that in favorable-odds situations, whether repeated or not, the optimal amount for an individual who maximizes his expected utility to invest will depend on his utility function. To promote your intuition, consider a polar case. A risk-neutral investor should invest his total wealth whenever he confronts a favorable-odds situation, as opposed to the “magic fraction” proposed by Kelly. Going all in, to use poker terminology, will maximize his expected total wealth, hence his expected utility, for any finite number of periods.²⁴ In short, Samuelson shows that the Kelly Criterion, though mathematically correct, should not guide an
23 Samuelson, Paul A. (1979). “Why We Should Not Make Mean Log of Wealth Big Though Years to Act Are Long,” Journal of Baking and Finance 3: 305-307.
24 http://www.investopedia.com/articles/trading/04/091504.asp. In an interesting coincidence, Elwyn Berlekamp, a distinguished Berkeley math professor who was Kelly’s research assistant, was an extremely successful investor in a brief stint managing a fund for Jim Simons. See footnote 19.
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investor’s actions, since it ignores the structure of preferences, whether risk neutral or risk averse.²⁵
Accounting for preferences, it turns out that the Kelly Criterion leads to precisely the right investment proportions if one’s utility function is logarithmic, but it is too conservative for less risk-averse utility functions, and vice versa. With logarithmic utility, one will just take an even money bet that either multiplies one’s wealth by 1+x or by 1/(1+x), for any x. Thus, one would take an even money bet to double or halve one’s wealth.
I lack both the space and capability to straighten out the sequential investment problem. But I should make a few observations to point out that even if the Kelly Criterion were correct, the formulation it employs does not capture most real world investment opportunities: (1) Most UU investments are illiquid for a significant period, often of unknown length. Monies invested today will not be available for reinvestment until they become liquid. (2) Markets charge enormous premiums to cash out illiquid assets.²⁶ (3) Models of optimal sequential investment strategies tend to assume away the most important real-world challenges to such strategies, such as uncertain lock-in periods. (4) There are substantial disagreements in the literature even about “toy problems,” such as those with immediate resolution of known-probability investments. The overall conclusion is that: (5) Money management is a challenging task in UU problems. It afflicts even those with a substantial edge when making such investments. And when the unknowable happens, as it did with the air-pocket plunge in the 1987 stock market or the 1997 Asian crisis, unforeseen short-term money-management problems – e.g., transferring monies across markets in time to beat margin calls – tend to emerge. These five points imply that even if it were clear how one should invest in a string of favorable gambles each of which is resolved instantaneously, that would help us little in the real world of UU investing, which presents a much more difficult task.
Though I have quibbled about the Kelly Criterion, it makes a simple, central point that is missed in virtually all investment advice. Most such advice
25 In the language of decision theory, individuals who follow Kelly rather than maximizing expected utility would be making a sacrifice in the certainty equivalent value of their terminal wealth, i.e., the wealth that results after participating in a string of gambles. The Kelly criterion is appropriate for someone with a logarithmic utility function.
26 For example, in real estate, a limited partnership interest that will come due in a few years is likely to sell about 30% below discounted expected future value. The significant discount reflects the complementary skills of acquirers, who must be able to assess and unlock the value of idiosyncratic partnerships. Personal communication, Eggert Dagbjartsson, Equity Resource Investments, December 2005. That firm earns substantial excess returns through its combination of effective evaluation of UU situations, and the unusual complementary skill of being able to deal effectively with recalcitrant general partners. Experience with Dagbjartsson’s firm – with which the author is associated – helped inspire this paper.
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focuses on efficient or near efficient markets, implying that one will not have a great edge in any investment. In contrast, the real world presents some ordinary investments, some attractive investments, and some very attractive investments. Clearly it makes sense to invest more in the more attractive investments. This leads to a maxim on investment advantage:
Maxim B: The greater is your expected return on an investment, that is the larger is your advantage, the greater the percentage of your capital you should put at risk.
Most investors understand this criterion intuitively, at least once it is pointed out. But they follow it insufficiently if at all. The investment on which they expect a 30% return gets little more funding than the one where they expect to earn 10%. Investment advantage should be as important as diversification concerns in determining how one distributes one’s portfolio.
IV. INVESTING WITH SOMEONE ON THE OTHER SIDE
One of the more puzzling aspects of the financial world is the volume of transactions in international currency markets. Average daily volume is $1.9 trillion, which is slightly more than all U.S. imports in a year. There are hedgers in these markets, to be sure, but their volume is many times dwarfed by transactions that cross with sophisticated or at least highly paid traders on both sides. Something no less magical than levitation is enabling all players to make money, or think that they are making money.
But let us turn to the micro situation, where you are trading against a single individual in what may or may not be a UU situation. If we find that people make severe mistakes in this arena even when there is merely risk or uncertainty, we should be much more concerned, at least for them, when UU may abound.
Bazerman-Samuelson example and lessons
Let us posit that you are 100% sure that an asset is worth more to you than to the person who holds it, indeed 50% more. But assume that she knows the true value to her, and that it is uniformly distributed on [0,100], that is, her value is equally likely to be 0, 1, 2, … 100. In a famous game due to Bazerman and Samuelson (1983), hereafter BS, you are to make a single bid. She will accept if she gets more than her own value. What should you bid?
When asked in the classroom, typical bids will be 50 or 60, and few will bid as low as 20. Students reason that the item will be worth 50 on average to her, hence 75 to them. They bid to get a tidy profit. The flaw in the reasoning is that the seller will only accept if she will make a profit. Let’s make you the bidder. If you offer 60, she will not sell if her value exceeds 60. This implies that her average value conditional on selling will be 30, which is the value of the average number from 0 to 60. Your expected value will be 1.5 times this amount, or 45. You will lose 15 on average, namely 60-45, when your bid is accepted. It is easy to show that any positive bid loses money in expectation. The moral of this story is that people, even people in decision analysis and finance classrooms, where these experiments have been run many times, are very poor at taking account of the decisions of people on the other side of the table.
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There is also a strong tendency to draw the wrong inference from this example, once its details are explained. Many people conclude that you should never deal with someone else who knows the true value, when you know only the distribution. In fact, BS offer an extreme example, almost the equivalent of an optical illusion. You might conclude that when your information is very diffuse and the other side knows for sure, you should not trade even if you have a strong absolute advantage.
That conclusion is wrong. For example, if the seller’s true value is uniform on [1,2] and you offer 2, you will buy the object for sure, and its expected value will be 1.5 times 1.5 = 2.25. The difference between this example and the one with the prior on [0,1] is that here the effective information discrepancy is much smaller. To see this, think of a uniform distribution from [100,101]; there is virtually no discrepancy. (In fact, bidding 2 is the optimal bid for the [1,2] example, but that the extreme bid is optimal also should not be generalized.)
Drawing inferences from others
The general lesson is that people are naturally very poor at drawing inferences from the fact that there is a willing seller on the other side of the market. Our instincts and early training lead us not to trust the other guy, because his interests so frequently diverge from ours. If someone is trying to convince you that his second hand car is wondrous, skepticism and valuing your own information highly helps. However, in their study of the heuristics that individuals employ to help them make decisions, Tversky and Kahneman (1974) discovered that individuals tend to extrapolate heuristics from situations where they make sense to those where they do not.
For example, we tend to distrust the other guy’s information even when he is on our side. This tendency has serious drawbacks if you consider sidecar investing – free riding on the superior capability of others – as we do below. Consider two symmetrically-situated partners with identical interests who start with an identical prior distribution about some value which is described by a two-parameter distribution. They each get some information on the value. They also have identical prior distributions on the information that each will receive. Thus, after his draw, each has a posterior mean and variance. Their goal is to take a decision whose payoff will depend on the true value. The individuals begin by submitting their best estimate, namely their means. After observing each other’s means, they then simultaneously submit their new best estimate. Obviously, if one had a tight (loose) posterior his estimate would shift more (less) toward that of his partner. In theory, two things should happen: (a) The two partners should jump over each other between the first and second submission half of the time. (b) The two partners should give precisely the same estimate for the third submission.
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In practice, unless the players are students of Robert Aumann²⁷ – his article “Agreeing to Disagree” (1976) inspired this example – rarely will they jump over each other. Moreover, on the third submission, they will not come close to convergence.
The moral of this story is that we are deeply inclined to trust our own information more than that of a counterpart, and are not well trained to know when this makes good sense, and when it inclines us to be a sucker. One should also be on the lookout for information disparities. Rarely are they revealed through carnival-barker behavior. For example, when a seller merely offers you an object at a price, or gets to accept or reject when you make a bid (as with BS), he will utilize information that you do not possess. You had better be alert and give full weight to its likely value, e.g., how much the object is worth on average were he to accept your bid.
In the financial world one is always playing in situations where the other fellow may have more information and you must be on your guard. But unless you have a strictly dominant action – i.e., it is superior no matter what the other guy’s information -- a maximin strategy will almost always push you never to invest. After all, his information could be just such to lead you to lose large amounts of money.
Two rays of light creep into this gloomy situation: First, only rarely will his information put you at severe disadvantage. Second, it is extremely unlikely that your counterpart is playing anything close to an optimal strategy. After all, if it is so hard for you to analyze, it can hardly be easy for him.²⁸
27 Robert Aumann and Thomas Schelling won the 2005 Nobel Memorial Prize in Economics for their contributions to game theory.
28 Given the potential for imperfect play, it is sometimes dangerous to draw inferences from the play of others, particularly when their preferences are hard to read. The Iraqi weapons of mass destruction provide a salient example. Many people were confident that such weapons were present not because of intelligence, but because they believed Saddam Hussein could have saved himself and his regime simply by letting in inspectors, who in the instance would find nothing.
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Absolute advantage and information asymmetry
It is helpful to break down these situations into two components. A potential buyer’s absolute advantage benefits both players. It represents the usual gains from trade. In many financial situations, as we observed above, a buyer’s absolute advantage stems from her complementary skills. An empty lot in A’s hands may be worth much less than it would be in B’s. Both gain if A trades to B, due to absolute advantage. But such an argument would not apply if A was speculating that the British pound would fall against the dollar when B was speculating that it would rise. There is no absolute advantage in such a situation, only information asymmetries.
If both parties recognize a pure asymmetric information situation, only the better informed player should participate. The appropriate drawing of inferences of “what-you-know-since-you-are-willing-to-trade” should lead to the well known no-trade equilibrium. Understanding this often leads even ordinary citizens to a shrewd strategem:
Maxim C: When information asymmetries may lead your counterpart to be concerned about trading with you, identify for her important areas where you have an absolute advantage from trading. You can also identify her absolute advantages, but she is more likely to know those already.
When you are the buyer, beware; seller-identified absolute advantages can be chimerical. For example, the seller in the bazaar is good at explaining why your special characteristics deserve a money-losing price – say it is the end of the day and he needs money to take home to his wife. The house seller who does not like the traffic noise in the morning may palter that he is moving closer to his job, suggesting absolute advantage since that is not important to you. Stores in tourist locales are always having “Going Out of Business Sales.” Most swindles operate because the swindled one thinks he is in the process of getting a steal deal from someone else.
If a game theorist had written a musical comedy, it would have been Guys and Dolls, filled as it is with the ploys and plots of small-time gamblers. The overseer of the roving craps game is Nathan Detroit. He is seeking action, and asks Sky Masterson – whose good looks and gambling success befit his name – to bet on yesterday’s cake sales at Lindy’s, a famed local deli. Sky declines and recounts a story to Nathan:
On the day when I left home to make my way in the world, my daddy took me to one side. “Son,” my daddy says to me, “I am sorry I am not able to bankroll you to a large start, but not having the necessary lettuce to get you rolling, instead I'm going to stake you to some very valuable advice. One of these days in your travels, a guy is going to show you a brand-new deck of cards on which the seal is not yet broken. Then this guy is going to offer to bet you that he can make the jack of spades jump out of this brand-new deck of cards and squirt cider in your ear. But, son, do not accept this bet, because as sure as you stand there, you're going to wind up with an ear full of cider.”
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In the financial world at least, a key consideration in dealing with UU situations is assessing what others are likely to know or not know. You are unlikely to have mystical powers to foresee the unforeseeable, but you may be able to estimate your understanding relative to that of others. Sky’s dad drew an inference from someone else’s willingness to bet. Presumably Ricardo was not a military expert, but just understood that bidders would be few and that the market would overdiscount the UU risk.
Competitive knowledge, uncertainty, and ignorance
Let us assume that you are neither the unusually skilled Buffett nor the unusually clear-thinking Ricardo. You are just an ordinary investor who gets opportunities and information from time to time. Your first task is to decide into which box an investment decision would fall. We start with unknown probabilities.
Investing with Uncertainty and Potential Asymmetric Information
| | Easy for Others to Estimate | Hard for Others to Estimate | |---|---|---| | Easy for You to Estimate | A. Tough markets | B. They’re the Sucker | | Hard for You to Estimate | C. Sky Masterson’s Dad, You’re the Sucker | D. Buffett’s Reinsurance Sale Calif. Earthquake Auth. |
The first row is welcome and relatively easy, for two reasons: (1) You probably have reasonable judgment of your knowledge relative to others, as would a major real estate developer considering deals in his home market. Thus you would have a good assessment of how likely you are to be in Box B or Box A. (2) If you are in Box B, you have the edge. Box A is the home of the typical thick financial market, where we tend to think prices are fair on average.
The second row is more interesting, and brings us to the subject matter of this paper. In Part V below, we will see Buffett sell a big hunk of reinsurance because he knew he was in box D. His premium was extremely favorable, and he knew that the likelihood of extreme odds-shifting information being possessed by the other side was thin. Box C consists of situations where you know little, and others may know a fair amount. The key to successfully dealing with situations where you find probabilities hard to estimate is to be able to assess whether others might be finding it easy.
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Be sensitive to telling signs that the other side knows more, such as a smart person offering too favorable odds. Indeed, if another sophisticated party is willing to bet, and he can’t know that you find probabilities hard to estimate, you should be suspicious. For he should have reasonable private knowledge so as to protect himself. The regress in such reasoning is infinite.
Maxim D: In a situation where probabilities may be hard for either side to assess, it may be sufficient to assess your knowledge relative to the party on the other side (perhaps the market).
Let us now turn to the more extreme case, situations where even the states of the world are unknown, as they would be for an angel investment in a completely new technology, or for insuring infrastructure against terrorism over a long period.
Investing with Ignorance and Potential Asymmetric Information
| | Known to Others | Unknown to Others | |---|---|---| | Unknown to You | E. Dangerous Waters Monday Morning Quarterback Risk | F. Low Competition Monday Morning Quarterback Risk |
In some ignorance situations, you may be confident that others know no better. That would place you in Box F, a box where most investors get deterred, and where the Buffetts of this world, and the Rothschilds of yesteryear have made lots of money. Investors are deterred because they employ a heuristic to stay away from UU situations, because they might be in E, even though a careful assessment would tell them that outcome was highly unlikely. In addition, both boxes carry the Monday Morning Quarterback (MMQ) risk; one might be blamed for a poor outcome if one invests in ignorance, when it was a good decision that got a bad outcome; might not have allowed for the fact that others might have had better knowledge when in fact they didn’t; or might not have allowed for the fact that others might have had better knowledge, when in fact they did, but that negative was outweighed by the positive of your absolute advantage. The criticisms are unmerited. But since significant losses were incurred, and knowledge was scant, the investment looks foolish in retrospect to all but the most sophisticated. An investor who could suffer significantly from any of these critiques might well be deterred from investing.
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Let us revisit the Gazprom lesson within this thought in mind. Suppose you are a Russia expert. It is still almost inevitable that real Russians know much more than you. What then should you do? The prudent course, it would seem, would be first to determine your MMQ risk. It may actually be reduced due to your largely irrelevant expertise. But if MMQ is considerable, steer clear. If not, and Russian insiders are really investing, capitalize on Box E, and make that sidecar investment. You have the additional advantage that few Westerners will be doing the same, and they are your prime competition for ADRs.²⁹
Speculation 3. UU situations offer great investment potential given the combination of information asymmetries and lack of competition.
Boxes E and F are also the situations where other players will be attempting to take advantage of us and, if it is our inclination, we might take advantage of them. This is the area where big money changes hands.
A key problem is to determine when you might be played for a sucker. Sometimes this is easy. Anyone who has small oil interests will have received many letters offering to buy, no doubt coming from people offering far less than fair value. They are monopsonists after all, and appropriately make offers well below the market. They may not even have any inside knowledge. But they are surely taking advantage of the impulsive or impatient among us, or those who do not understand the concepts in this paper.
Being a possible sucker may be an advantage if you can gauge the probability. People are strongly averse to being betrayed. They demand much stronger odds when a betraying human rather than an indifferent nature would be the cause of a loss (Bohnet and Zeckhauser, 2004). Given that, where betrayal is a risk, potential payoffs will be too high relative to what rational decision analysis would prescribe.
Investing in UU with potentially informed players on the other side
Though you may confront a UU situation, the party or parties on the other side may be well informed. Usually you will not know whether they are. Gamblers opine that if you do not know who the sucker is in a game that you are the sucker. That does not automatically apply with UU investments. First, the other side may also be uninformed. For example, if you buy a partially completed shopping center, it may be that the developer really did run out of money (the proffered explanation
29 In January 2006, Gazprom traded in the west as an ADR, but soon became an over-the-counter stock.
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for its status) as opposed to his discovery of deep tenant reluctance. Second, you may have a complementary skill, e.g., strong relations with WalMart, that may give you a significant absolute advantage multiple.
The advantage multiple versus selection formula
Let us simplify and leave risk aversion and money management matters aside. Further posit, following BS, that you are able to make a credible take-it-or-leave-it offer of 1. The value of the asset to him is v, an unknown quantity. The value to you is av, where a is your absolute advantage. Your subjective prior probability distribution on v is f(v). The mean value of your prior is m < 1.³⁰ In a stripped-down model, three parameters describe this situation: your advantage multiple, a; the probability that the other side is informed, p; and the selection factor against you, s, if the other side is informed.³¹ Thus s is the fraction of expected value that will apply, on average, if the other side is informed, and therefore only sells when the asset has low value to her. Of course, given the UU situation, you do not know s, but you should rely on your mean value of your subjective distribution for that parameter.
If you knew p = 0, that the other side knew no more than you, you would simply make the offer if am > 1. If you knew there were selection, i.e., p = 1, you would invest if your multiple more than compensated for selection, namely if ams > 1. The general formula is that your return will be:
am[ps + (1-p)1] .
(1)
Maxim E: A significant absolute advantage offers some protection against potential selection. You should invest in a UU world if your advantage multiple is great, unless the probability is high the other side is informed and if, in addition, the expected selection factor is severe.
Following Maxim E, you should make your offer when the expression in (1) exceeds 1.
In practice, you will have a choice of offer, t. Thus, s will vary with t, i.e., s(t).³² The payoff for any t will be
am[ps(t) + (1-p)1] - t. (2)
30 It is important that m < 1. Otherwise the seller would refuse your offer if he were uninformed.
31 In health care, this process is called adverse selection, with sicker people tending to enroll in more generous health plans.
32 Let v be the conditional mean of x < v. The value of s will be constant if v/v = positive k for all v. This will be the case if f(v) is homogeneous, i.e., f(kv) = knf(v), as with the uniform or triangular distribution starting at 0.
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If at the optimal offer t*, this quantity is positive, you should offer t*.
Playing the advantage multiple versus selection game
Our formulation posited a take-it-or-leave-it offer with no communication. In fact, most important financial exchanges have rounds of subtle back-and-forth discussion. This is not simply cheap talk. Sometimes real information is provided, e.g., accounting statements, geological reports, antique authentications. And offers by each side reveal information as well. Players on both sides know that information asymmetry is an enemy to both, as in any agency problem.
It is well known that if revealed information can be verified, and if the buyer knows on what dimensions information will be helpful, then by an unraveling argument all information gets revealed.³³ Consider a one-dimension case where a value can be between 1 and 100. A seller with a 100 would surely reveal, implying the best unrevealed information would be 99. But then the 99 would reveal, and so on down through 2.
When the buyer is in a UU situation, unraveling does not occur, since he does not know the relevant dimensions. The seller will keep private unfavorable information on dimensions unknown to the buyer. She will engage in signposting: announcing favorable information, suppressing unfavorable.³⁴
The advantage multiple versus selection game will usually proceed with the seller explaining why she does not have private information, or revealing private information indicating that m and a are large. Still, many favorable deals will not get done, because the less informed party can not assess what it does not know. Both sides lose ex ante when there will be asymmetry on common value information, or when, as in virtually all UU situations, asymmetry is suspected.
Auctions as UU games
Auctions have exploded as mechanisms to sell everything from the communications spectrum to corporate securities. Economic analyses of auctions – how to conduct them and how to bid – have exploded alongside. The usual format is that an informed seller faces a group of less knowing buyers. The
33 See Grossman (1981) on unraveling. If information is costly to reveal, then less favorable information is held back and signposting applies (Zeckhauser and Marks, 1996).
34 To be sure, the shrewd buyer can deduce: “Given the number of unknown dimensions I suspected, the seller has revealed relatively few.” Hence, I assume that there are a number of unfavorable dimensions, etc. When seller revelation is brief, only high m buyers will make exchanges. The doubly shrewd buyer may be informed or get informed on some dimension without the seller knowing which. He can then say: “I have unfavorable information on a dimension. Unless you reveal on all dimensions, this information will stay private, and I will know that you are suppressing information.” The triply shrewd buyer, knowing nothing, will make the same statement. The shrewd seller has countermeasures, such as insisting on proof that the buyer is informed, e.g., by third party attestation, and if evidence is received then revealing some but not all, hoping to hit the lucky dimension.
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usual prescription is that the seller should reveal his information about elements that will affect all buyers’ valuations, e.g., geologic information on an oil lease or evidence of an antique’s pedigree, to remove buyers’ concerns about the Winner’s Curse. The Winner’s Curse applies when an object, such as an oil lease, is worth roughly the same to all. The high bidder should be aware that every other bidder thought it was worth less than he did. Hence, his estimate is too high, and he is cursed for winning.
Real world auctions are often much more complex. Even the rules of the game may not be known. Consider the common contemporary auction phenomenon, witnessed often with house sales in hot markets, and at times with the sale of corporations.³⁵ The winner, who expected the final outcome to have been determined after one round of bidding, may be told there will be a best and final offer round, or that now she can negotiate a deal for the item.
Usually the owner of the object establishes the rules of the game. In theory, potential buyers would insist that they know the rules. In practice, they often have not. When Recovery Engineering, makers of PUR water purifiers, was sold in 1999, a “no one knows the rules” process ensued, with Morgan Stanley representing the seller. A preliminary auction was held on an August Monday. Procter and Gamble (P&G) and Gillette bid, and a third company expressed interest but said it had difficulties putting its bid together. Gillette’s bid was $27 per share; P&G’s was $22. P&G was told by the investment banker that it would have to improve its bid substantially. Presumably, Gillette was told little, but drew appropriate inferences, namely that it was by far high. The final auction was scheduled for that Friday at noon. Merrill Lynch, Gillette’s investment banker, called early on Friday requesting a number of additional pieces of due diligence information, and requesting a delay till Monday. Part of the information was released – Gillette had had months to request it – and the auction was delayed till 5 p.m. Friday. P&G bid $34. At 5 p.m., Merrill Lynch called, desperate, saying it could not get in touch with Gillette. Brief extensions were granted, but contact could not be established. P&G was told that it was the high bidder. Over the weekend a final deal was negotiated at a slightly higher price; the $300 million deal concluded. But would there have been a third round of auction if Gillette had bid $33.50 that Friday? No one knows.
The Recovery board puzzled over the unknowable question: What happened to Gillette? One possibility was that Gillette inferred from the fact that it was not told its Monday bid was low that it was in fact way above other bidders. It was simply waiting for a deal to be announced, and then would propose a price
35 See Subramanian and Zeckhauser (2004), who apply the term “negotiauctions” to such processes.
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perhaps $2 higher, rather than bid and end up $5 higher.³⁶ Gillette never came back. A while later, Recovery learned that Gillette was having – to that time unreported – financial difficulties. Presumably, at the moment of truth Gillette concluded that it was not the time to purchase a new business. In short, this was a game of unknowable rules, and unknowable strategies.³⁷ Not unusual.
At the close of 2005, Citigroup made the winning bid of about $3 billion for 85% of the Guangdong Development Bank, a financially troubled state-owned Chinese bank. As the New York Times reported the deal, it “won the right to negotiate with the bank to buy the stake.” If successful there, its “control might allow Citigroup to install some new management and have some control over the bank’s future…one of the most destitute of China’s big banks…overrun by bad loans.”³⁸ Citigroup is investing in a UU situation, and knows that both the rules of the game and what it will win are somewhat undefined. But it is probably confident that other bidders were no better informed, and that both the bank and the Chinese government (which must approve the deal) may also not know the value of the bank, and were eager to secure foreign control. Great value may come from buying a pig in a poke, if others also can not open the bag.
Ideal investments with high and low payoffs
In many UU situations, even the events associated with future payoff levels – for example, whether a technology supplier produces a breakthrough or a new product emerges – are hard to foresee. The common solution in investment deals is to provide for distributions of the pie that depend not on what actually happens, but solely on money received. This would seem to simplify matters, but even in such situations sophisticated investors frequently get confused.
With venture capital in high tech, for example, it is not uncommon for those providing the capital to have a contractual claim to all the assets should the venture go belly up. Similarly, “cram down” financings, which frequently follow when startups underperform, often gives VCs a big boost in ownership share. In theory, such practices could provide strong incentives to the firm’s managers. In reality, the managers’ incentives are already enormous. Typical VC arrangements given bad outcomes cause serious ill will, and distort incentives – for example, they reward gambling behavior by managers after a bleak streak. Worse still for the VCs, they are increasing their share of the company substantially when the
36 Recovery created a countermeasure to raise any post-deal bid by inserting a breakup fee in its deal with P&G that declined (ultimately to 0) with the price premium paid by a new buyer.
37 Details confirmed by Brian Sullivan, then CEO of Recovery Engineering, in personal communication, January 2006. Zeckhauser was on the Recovery board due to a sidecar privilege. He had been Sullivan’s teacher, and had gotten him the job.
38 New York Times, December 31, 2005, B1 and B4. Citigroup had several Chinese state-owned companies as partners, but they probably gave more political cover than knowledge of the value of the bank.
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company is not worth much. They might do far better if arrangements specified that they sacrifice ownership share if matters turn out poorly, but gain share if the firm does particularly well.
Maxim F: In UU situations, even sophisticated investors tend to underweight how strongly the value of assets varies. The goal should be to get good payoffs when the value of assets is high.
No doubt Ricardo also took Maxim F into account when he purchased the “Waterloo bonds.” He knew that English money would be far more valuable if Wellington was victorious and his bonds soared in value, than if he lost and the bonds plummeted.
A UU investment problem
Now for a harder decision. Look at the letter in Exhibit A, which offers you the chance to make a modest investment in an oil well. You have never heard of Davis Oil and the letter came out of the blue, but you inquire and find out that it is the company previously owned by the famous, recently deceased oilman Marvin Davis. Your interest is offered because the Davis Company bought the managing partner’s interest in the prospect from a good friend and oil man who invited you into his prospect.³⁹ Davis is legally required to make this offer to you. Decide whether to invest or merely wait for your costless override before you read on.
39 That man was Malcolm Brachman, president of Northwest Oil, a bridge teammate and close friend. Sadly Malcolm had died in the interim. One consequence was that he could not advise you.
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EXHIBIT A
The exhibit appears in the article as a scanned image of the original letter; the text below is a transcription of that image.
September 19, 2005
WORKING INTEREST OWNER: Richard Zeckhauser
Re: Well Proposal
Davis Petroleum Corp.
Devlin #1-12
Section 12-T8N-R19W
Washita County, Oklahoma
Gentlemen:
Davis Petroleum Corp. (“Davis”) proposes the drilling of a 17,000’ Sub-Thrusted Springer test at a surface location of 660’ FNL and 1980’ FWL and a bottom hole location of 1,650’ FNL and 990’ FWL of Section 12-T8N-R19W, Washita County, Oklahoma. Enclosed for your review is our AFE reflecting estimated dry hole costs of $6,869,100.00 and estimated completion costs of $2,745,400.00. As a working interest owner within the referenced unit and per the terms and conditions of that certain Order 450325, Cause CD 200100725-T, dated March 29, 2001, Davis respectfully requests that you elect one of the afforded options as follows:
1. Participate in the drilling and completing of said well by paying your proportionate share of well costs as stipulated by Order 450325;
2. Elect not to participate in the proposed test well, electing to farmout your unit interest delivering to Davis your interest at a proportionate 75% net revenue interest.
Per the terms of Order 450325 you have 15 days upon receipt of this proposal to make your election as outlined above. Failure to respond within the 15 day period will evidence your election not to participate thus relinquishing your interest under paragraph 2. above.
Please indicate the option of your choice by signing below and returning one copy of this letter to my attention. This proposal may be terminated without further notice. Should you have any questions, please contact me at (713) 439-6750 or Bill Jaqua at (405) 329-0779.
Sincerely,
Davis Petroleum Corp.
Alan Martinkewiz
Landman
THE UNDERSIGNED HEREBY ACCEPTS OPTION NO. \_\_\_\_\_\_, THIS \_\_\_\_\_\_ DAY OF \_\_\_\_\_\_\_\_, 2005
By: \_\_\_\_\_\_\_\_\_\_
Title: \_\_\_\_\_\_\_\_\_\_
Company: \_\_\_\_\_\_\_\_\_\_
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Here is what your author did. He started by assessing the situation. Davis could not exclude him, and clearly did not need his modest investment. The letter provided virtually no information, and was not even put on letterhead, presumably the favored Davis approach if it were trying to discourage investment. Davis had obviously spent a fair amount of effort determining whether to drill the well, and decided to go ahead. It must think its prospects were good, and you would be investing as a near partner.
Bearing this in mind, he called Bill Jaqua – a contact Davis identified in the letter – and asked about the well. He was informed it was a pure wildcat, and that it was impossible to guess the probability of success. Some geologic technical discussion followed, which he tried to pretend he understood. He then asked what percent of Davis wildcat wells had been successful in recent years, and got a number of 20-25%. He then asked what the payoff was on average if the wells were successful. The answer was 10 to 1. Beyond that, if this well was successful, there would be a number of other wells drilled in the field. Only participation now would give one the right to be a future partner, when presumably the odds would be much more favorable. This appeared to be a reasonably favorable investment, with a healthy upside option of future wells attached. The clinching argument was that Jaqua courteously explained that Davis would be happy to take his interest and give him the free override, thus reinforcing the message of the uninformative letter not placed on letterhead. (It turned out that the override would have only been 1% of revenue -- an amount not mentioned in the letter – as opposed to 76% if he invested.)⁴⁰ In short, the structure of the situation, and the nature of Davis’s play made a sidecar investment imperative. The well has not yet been started.
Davis was in a tough situation. It had to invite in undesired partners on favorable terms when it had done all the work. It reversed the usual ploy where someone with a significant informational advantage tries to play innocent or worse, invoke some absolute advantage story. Davis tried to play up the UU aspect of the situation to discourage participation.
Review of the bidding
You have been asked to address some decision problems. Go back now and grade yourself first on the overconfidence questionnaire. The answers are in the footnote.⁴¹
You were asked about three investments: Tengion, Gazprom and Davis Oil. Gazprom has done nicely over a six-month period. Neither of the other outcomes has been determined. Go back and reconsider your choices, and decide
40 Not mentioned in the letter was that 24% went off the top to priority claims, and that Davis charges 75% if you take the free override.
41 1) 173,710 2) 2,716 3) 2,007,901 4) 130,119 5) 13 6) 12,212,000 7) $259B 8) 13.45% 9) 853,000
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whether you employed the appropriate principles when making them, and then assess the more general implications for investment in UU situations. Though this essay pointed out pitfalls with UU investing, it was generally upbeat about the potential profits that reside in UU arenas. Hopefully you have been influenced, at least a bit.
V. A BUFFETT TALE
The following story encapsulates the fear of UU situations, even by sophisticated investors, and the potential for shrewd investors to take great advantage of such situations. In 1996, I was attending an NBER conference on insurance. One participant was the prime consultant to the California Earthquake Authority. He had been trying to buy a $1 billion slice of reinsurance – to take effect after $5 billion in aggregate insured losses -- from the New York financial community. The Authority was offering five times estimated actuarial value, but had no takers. It seemed exceedingly unlikely that the parties requesting coverage had inside information that a disastrous earthquake was likely. Hence, there was a big advantage, in effect a = 5, and p was close to 0. Maxim E – weigh absolute advantage against informational disadvantage – surely applied.
My dinner table syndicate swung into action, but ended up $999.9 million short. A couple days later, we learned that Buffett had flown to California to take the entire slice. Here is his explanation.
…we wrote a policy for the California Earthquake Authority that goes into effect on April 1, 1997, and that exposes us to a loss more than twice that possible under the Florida contract. Again we retained all the risk for our own account. Large as these coverages are, Berkshire's after-tax "worst-case" loss from a true mega-catastrophe is probably no more than $600 million, which is less than 3% of our book value and 1.5% of our market value. To gain some perspective on this exposure, look at the table on page 2 and note the much greater volatility that security markets have delivered us. [Chairman’s letter to the Shareholders of Berkshire Hathaway, 1996, http://www.ifa.com/Library/Buffet.html]⁴²
Reinsurance for earthquakes is certainly a venture into the unknown, but had many attractive features beyond its dramatic overpricing. Unlike most insurance, it was exceedingly unlikely that the parties taking insurance had inside knowledge on their risk. Thus, Buffett – despite attention to money management -- was willing to take 100% of a risk of which Wall Street firms houses rejected taking even part. Those fancy financial entities were not well equipped to take a risk on something that was hard for them to estimate. Perhaps they did not recognize that others had no inside information, that everyone was operating with the same probability. And perhaps they were just concerned about Monday Morning Quarterbacking.
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It is also instructive to consider Buffett’s approach to assessing the probabilities in this UU situation, as revealed in the same annual report:
So what are the true odds of our having to make a payout during the policy's term? We don't know - nor do we think computer models will help us, since we believe the precision they project is a chimera. In fact, such models can lull decision-makers into a false sense of security and thereby increase their chances of making a really huge mistake. We've already seen such debacles in both insurance and investments. Witness "portfolio insurance," whose destructive effects in the 1987 market crash led one wag to observe that it was the computers that should have been jumping out of windows.
Buffett was basically saying to Wall Street firms: “Even if you hire 100 brilliant Ph.D.s to run your models, no sensible estimate will emerge.” These are precisely the types of UU situations where the competition will be thin, the odds likely favorable, and the Buffetts of this world can thrive.
As Buffett has shown on repeated occasions, a multi-billionaire will rush in where mathematical wizards fear to tread. Indeed, that explains much of his success. In 2006 hurricane insurance met two Buffett desiderata, high prices and reluctant competitors. So he plunged into the market:
Buffett’s prices are as much as 20 times higher than the rates prevalent a year ago, said Kevin Madden, an insurance broker at Aon Corp. in New York. On some policies, premiums equal half of its maximum potential payout, he said. [In a May 7, 2006, interview Buffett said:] “We will do more than anybody else if the price is right… We are certainly willing to lose $6 billion on a single event. I hope we don’t.'’ http://seekingalpha.com/article/11697
At least two important lessons emerge from thinking about the “advantage-versus-selection” problem, and observing Warren Buffett:
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Maxim G: Discounting for ambiguity is a natural tendency that should be overcome, just as should be overeating.
Maxim H: Do not engage in the heuristic reasoning that just because you do not know the risk, others do. Think carefully, and assess whether they are likely to know more than you. When the odds are extremely favorable, sometimes it pays to gamble on the unknown, even though there is some chance that people on the other side may know more than you.
Buffett took another bold financial move in 2006, in a quite different field, namely philanthropy. He announced that he would give away 85% of his fortune or $37.4 billion, with $31 billion going to the Bill and Melinda Gates Foundation. Putting money with the Gates Foundation represents sidecar philanthropy. The Foundation is an extremely effective organization that focuses on health care and learning. It is soon to be led by Bill Gates, a fellow with creativity, vision and hardheadedness as strong complementary skills, skills which are as valuable in philanthropy as they are in business.
VI. CONCLUSION
This essay offers more speculations than conclusions, and provides anecdotal accounts rather than definitive data. Its theory is often tentative and implicit. But the question it seeks to answer is clear: How can one invest rationally in UU situations? The question sounds almost like an oxymoron. Yet clear thinking about UU situations, which includes prior diagnosis of their elements, and relevant practice with simulated situations, may vastly improve investment decisions where UU events are involved. If they do improve, such clear thinking will yield substantial benefits. For financial decisions at least, the benefits may be far greater than are available in run-of-the-mill contexts, since competition may be limited and prices well out of line.
How important are UU events in the great scheme of financial affairs? That itself is a UU question. But if we include only those that primarily affect individuals, the magnitude is far greater than what our news accounts would suggest. Learning to invest more wisely in a UU world may be the most promising way to significantly bolster your prosperity.
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APPENDIX A
Assessing Quantities*
- Democratic votes in Montana, 2004 Presidential election
- Length of Congo River (in miles)
- Number of subscribers to Field and Stream
- Area of Finland (in square miles)
- Birth rate in France per 1,000 population
- Population of Cambodia
- Revenues of Wal-Mart Stores (largest in U.S.), 2003
- Annual Percent Yields on 30-Year Treasury Bonds in 1981 (This year had the highest rate over the 1980-1998 period.)
- Number of physicians in the United States, 2002
- Number of electoral votes going to Republican presidential candidate in 2008 (out of 538)
- Value of Dow Jones Average on December 31, 2006 (on 6/30/06 closed at 11,150)
- Value of the NASDAQ on December 31, 2006 (on 6/30/06 closed at 2,172)
| | 1st %ile | 25th %ile | 50th %ile | 75th %ile | 99th %ile | |---|---|---|---|---|---| | Democratic votes MT 2004 Pres. election | | | | | | | Congo River (length in miles) | | | | | | | Field & Stream (number of subscribers) | | | | | | | Finland (area in square miles) | | | | | | | Birth Rate of France (per thousand) | | | | | | | Population of Cambodia | | | | | | | Revenues of Wal-Mart Stores, 2003 | | | | | | | % Yields on 30-Year Bonds, 1981 | | | | | | | Number of Physicians in U.S., 2002 | | | | | | | # electoral college votes, Republican presidential candidate in 2008 | | | | | | | Dow Jones Average 12/31/06 (on 6/30/06 closed at 11,150) | | | | | | | Value of NASDAQ 12/31/06 (on 6/30/06 closed at 2,172) | | | | | |
* Question 1, http://www.uselectionatlas.org/RESULTS/state.php?f=0&year=2004&fips=30. Questions 2-6, 1995 Information Please Almanac. Question 8, 1999 Wall Street Journal Almanac. Questions 7 & 9, World Almanac 2005.
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