The wisdom of crowds” has become a modern cliché. And a strange one — the crowds that attended the Nuremberg Rallies, or cheered the tumbrils of the Reign² of Terror, were anything but wise. Many adjectives might be applied³ to the assemblies that gather to applaud Dear Leader Kim Jong Un or cheer Chelsea Football Club — but “wise” is not one. Anyone standing⁴ back from these events must ask themselves a question: how could large numbers of people, so similar to ourselves, behave like that? What on earth were they thinking?

“群体的智慧”已变成了一个现代陈词滥调。它也是一种奇怪的说法——那些参加纽伦堡党代会（Nuremberg Rallies，1923至1938年期间纳粹党一年一度的集会——译者注）的人、“雅各宾专政”(Reign of Terror)时期那些在囚车旁欢呼的人，都根本毫无判断力。许多形容词可能都适用于描述一群聚集在一起、为“亲爱的领袖”金正恩(Kim Jong Un)鼓掌或是为切尔西足球俱乐部(Chelsea Football Club)欢呼的人，但“有判断力”绝非其中之一。任何未参加过这些活动的人都必须问自己一个问题：为何这么多和我们如此相像的人会有那样的表现？他们究竟在想什么？

There is considerable research on the factors that influence the behaviour of crowds. We experience a need to affirm group or tribal⁵ identities — a fact that is often exploited by unscrupulous or mentally unbalanced leaders. Groups of people with similar opinions reinforce each other’s positions, encouraging one another to adopt ever moreextreme views. The answer to the question “what were they thinking?” is that, mostly, they were not thinking at all. That is often the nature of social behaviour.

关于影响群体行为的因素，有相当多的研究。我们有确认自己群体或部落身份的现实需求，但这一点经常被不择手段或精神有问题的领导人所利用。拥有相似观点的群体成员会强化彼此的观点，促使彼此的观点更加极端化。“他们在想什么？”——这个问题的答案是：大多数时候，他们根本没有在思考。这通常就是群体行为的本质。

So how did the phrase “wisdom of crowds” come into being? It is an expression of the mathematical property that an average of many independent estimates of the same variable has a lower expected error than the individual estimates themselves. That was the context of the example which James Surowecki used to introduce the idea in his widely read book of the same name, citing the distinguished⁶ mathematician⁷ Francis Galton’s observations at an ox weighing competition (actually, Galton was concerned with the median rather than the mean estimate, but let that technical detail pass).

那么，“群体的智慧”这一说法又是如何产生的呢？它表达的其实是一种数学特性，即对同一变量的许多独立判断的平均值比个人自己判断的预期错误率要低。这就是詹姆斯•苏罗维奇(James Surowecki)在他那本广为传阅的同名书《群体的智慧》(wisdom of crowds)中所援引那个例子的背景。苏罗维奇援引的是著名数学家弗朗西斯•高尔顿(Francis Galton)对一场猜测一头公牛重量比赛的观察（实际上，高尔顿关注的是中位数而非平均估值，但这里忽略这一技术细节），从而提出了群体有智慧的观点。

It is entirely⁸ rational to adopt the common opinion on a subject about which one knows little; I believe the earth is round because that is the balance of informed opinion, and would a millennium⁹ ago have believed it to be flat, for the same reason. But the number of practical situations in which this statistical¹⁰ property is useful is severely¹¹ limited. It is usually better to direct one’s efforts at reducing the error of estimates rather than increasing the number of erroneous estimates. That is why we prefer to entrust¹² the navigation of a plane to a skilled pilot instead of using the average of the opinions of the passengers.

在一个自己不甚了解的问题上接受公认的看法是完全明智的；我相信地球是圆的，因为这一结论是主流权威观点，而出于同样的原因，1000年前的人们曾经相信它是平的。但能让这种统计特性能发挥作用的现实情形是非常有限的。通常情况下，更好的办法是去努力减少估计中的错误，而非增加错误估计的数量。这就是为什么我们更愿意将开飞机的任务托付给熟练的飞行员，而不是综合采纳大多数乘客的意见。

The wisdom of crowds becomes a pathology when the estimates of the members of the crowd cease to be independent of each other, and this is likely when the crowd is large, ill-informed, or both. It is in the nature of a crowd to turn on anyone who dissents¹³ from what is already the average opinion. This is equally true on the streets of revolutionary Paris, the squares of Pyongyang, and the terraces of Chelsea Football Club.

当每个群体成员的判断不再是相互独立的，群体的智慧就会变得病态。当群体数量庞大、信息不灵通（或两者兼有)时，这种情况更可能出现。群体的本性决定了，任何与既有主流观点意见相左的人都会受到群体的攻击。在大革命时期的巴黎街头、在平壤的广场上，以及在切尔西俱乐部的看台上，情况都是如此。

Or on the trading floor of an investment bank. The supposed wisdom of crowds is used as a justification¹⁴ for claims of market efficiency, crudely expressed in slogans such as “the market knows best” and “you can’t buck¹⁵ the market”. At a sophisticated level, the idea provides a rationale for a regulatory philosophy that attempts to reproduce the conditions required for the validity of Galton’s result — the existence of many independent estimates of the same variable.

这种情形同样适用于投资银行的交易大厅。所谓群体有智慧的观点被当作支持市场有效论的理由，并被简单地总结为“市场最权威”和“你不能逆市而为”等口号。说得复杂一点，群体有智慧的观点则为一种监管理念提供了理由，这种理念试图复制证实高尔顿观察结果（即存在对同一变量的许多种独立估算）所必需的条件。

So we aim to promote a trading environment characterised by many conflicting assessments¹⁶ of the value of a security based on identical — and therefore necessarily limited — information about the value of securities. The belief that an aggregate¹⁷ of casual opinions provides a better process of value discovery than a flow of informed judgment¹⁸ through close engagement by investors¹⁹, is an article of faith rather than a matter of empirical evidence.

因此，我们的目标是推动这样一种交易环境，它的特点是，基于相同（因此也是有限的）信息，对一支证券的价值存在许多种不一致的评估。有人认为，与投资者通过密切关注而产生的大量明智判断相比，随机观点的汇总能更好地发现价值，这种看法只是一种信念，缺乏经验证据的支持。

Galton wrote of the wisdom of crowds. The still more distinguished mathematician Isaac Newton, after losing vast sums investing in the South Sea bubble, wrote more wisely of their madness.

高尔顿描写了群体的智慧。一位更著名的数学家艾萨克•牛顿(Isaac Newton)在南海股票泡沫中损失大笔资金之后，更明智地描绘了他们的疯狂。