经济学不科学
作者：英国《金融时报》专栏作家约翰•凯2010-04-26
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中国电信博物馆4月的第二个周末，一群非常杰出的经济学家汇聚一堂，参加了由乔治•索罗斯(George Soros)倡议的新经济思维研究所(Institute for New Economic Thinking)创立
大会。面对最近这场危机中经济学的失败之处，他们扪心自问。失败在两个领域最为明显：现代金融经济学的基石——有效市场假说的失效，以及近代宏观经济学理论的无用。左炔诺孕酮片
桶装方便面有效市场假说的核心思想是，价格是估算资产潜在价值的最佳表现形式。这个论点最近遭遇重创。美国房地产泡沫促成了货币市场的繁荣与萧条。在泡沫之前，“新经济”一败涂地，而长期资本管理公司(Long-Term Capital Management)也几近崩溃，这家对冲基金从一开始就是金融经济学复杂性的最佳例证。
而当前高等经济学中教授的宏观经济学大体上是基于一种名为动态随机一般均衡(DSGE)的分析模式。这个乏味的名字本身就泄漏了天机：理论家们大多是在自说自话。在预测危机、分析危机进展和提供应对措施建议方面，他们的理论几乎一无是处。
近期的经济政策激辩不仅在很大程度上忽视了动态随机一般均衡模型，而且与上世纪30年代的经济政策之辩有着惊人的相似之处，尽管最终的解决方式有所不同。被引用最
多的经济学家是约翰•梅纳德•凯恩斯(John Maynard Keynes)和海曼•明斯基(Hyman Minsky)，两者都已去世。
无论是有效市场假设还是动态随机一般均衡模型，都与理性预期的概念有关——大概可以如下描述这个概念，即家庭和企业在做经济决定时仿佛掌握着关于这个世界的一切可知信息。如果你纳闷为何这样一种难以置信的理念会被普遍接受，部分原因在于它的保守含义。根据理性预期理论，公司和家庭不仅与决策者知道的一样多，而且还能预料到政府的行动，因此政府做到最好也不过是维持自身的可预测性。大多数经济政策都是无效的。
自由市场中的大部分干预手段亦是如此。有人认为那些购买次贷或基于次贷的证券化产品的人之所以这么做是因为掌握的信息比卖家少，这种观点是没有存在空间的。当高盛(Goldman Sachs)的男男女女做着“上帝的工作”时，他们赚得的利润并非来自信息优势，而是他们服务的价值。政府在经济中扮演的角色是保证市场运转。
这些理论的吸引力远远超越了富人和保守派阶层，其中有着更深层次的原因。如果说有一种简单的、单一的、放诸四海而皆准的经济行为学理论，那么由理性预期、有效市场假说和动态随机一般均衡模型所组成的那一套论点就是那种理论。任何其他描述这个世界的方式都必须认识到人们的行动由他们的信念和感知（难免会出错）所决定，必须承认一
切皆无定数，必须适应行动对于不断变化的社会及文化准则的依赖。这样一来，经济模型就无法放诸四海而皆准：它们必须因地制宜。
标准方法有着科学的外表，因为它能根据少数几种原理得出清晰的预测。但这只是表象而已，因为这些预测往往是错误的。在投资者和决策者所面对的真实环境中，行动确实取决于信念和感知、必须应对不确定性、也是社会背景的产物。没有什么放诸四海而皆准的经济理论，而新经济思维必然应该是兼收并蓄的。这种见解就是凯恩斯最伟大的遗产。
约翰•凯是新经济思维研究所顾问委员会成员之一。
Economics may be dismal, but it is not a science
By John Kay 2010-04-26
A remarkably distinguished group of economists gathered last weekend for the inaugural conference of the Institute for New Economic Thinking, an initiative of George Soros. They were soul arching over the failures of economics in the recent crisis. Such failures are most evident in two areas: the inadequacies of the efficient market hypothesis, the bedrock of modern financial economics, and the irrelevance of recent macroeconomic theory.
安全知识答题大骆
The central idea of the efficient market hypothesis is that prices reprent the best estimate of the underlying value of asts. This thesis has recently taken a battering. The boom and bust in the money markets was precipitated by a US housing bubble. That bubble followed the New Economy fiasco and was preceded by the near-failure of Long Term Capital Management, a hedge fund designed to showca sophisticated financial economics.
孕吐从第几周开始
The macroeconomics taught in advanced economics today is largely bad on analysis labelled dynamic stochastic general equilibrium. The unappealing
title gives the game away: the theorists are mostly talking to themlves. Their theories proved virtually uless in anticipating the crisis, analysing its development and recommending measures to deal with it.
Recent economic policy debates have not only largely ignored DSGE, but have also been remarkably similar to the economic policy debates of the 1930s, although they have been resolved differently. The economists quoted most often are John Maynard Keynes and Hyman Minsky, both of whom are dead.
Both the efficient market hypothesis and DSGE are associated with the idea of rational expectations -
which might be described as the idea that
houholds and companies make economic decisions as if they had available to them all the information about the world that might be available. If you wonder why such an implausible notion has won wide acceptance, part of the explanation lies in its conrvative implications. Under rational expectations, not only do firms and houholds know already as much as policymakers, but
they also anticipate what the government itlf will do, so the best thing government can do is to remain predictable. Most economic policy is futile.
So is most interference in free markets. There is no room for the notion that people bought subprime mortgages or curitid products bad on them becau they knew less than the people who sold them. When the men and women
梦见工作of Goldman Sachs perform "God's work", the profits they make come not from information advantages, but from the value of their rvices. The economic
role of government is to keep markets working.
The theories have appeal beyond the ranks of the rich and conrvative
for a deeper reason. If there were a simple, single, universal theory of economic behaviour, then the suite of arguments comprising rational expectations, efficient markets and DSEG would be that theory. Any other way
of describing the world would have to recogni that what people do depends on their fallible beliefs and perceptions, would have to acknowledge uncertainty, and would accommodate the dependence of actions on changing social and
cultural norms. Models could not then be universal: they would have to be specific to contexts.
The standard approach has the appearance of science in its ability to generate clear predictions from a small number of axioms. But only the appearance, since the predictions are mostly fal. The environment actually faced by investors and economic policymakers is one in which actions do depend on beliefs and perceptions, must deal with uncertainty and are the product of a social context. There is no universal economic theory, and new economic thinking must necessarily be eclectic. That insight is Keynes's greatest legacy.
John Kay is a member of the advisory board of the Institute for New Economic Thinking
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