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��价格是否合理的问题，但是很少研究给定现实世界的基本面比如说收益，某资产价格是否合理的问题。后一问题看似明显，其实不易回答。萨默斯，现为奥巴马政府头号经济顾问，曾经用一个“番茄酱经济学家”的比喻嘲讽过金融学教授—番茄酱经济学家“证明了两夸脱瓶装的番茄酱所卖价格刚好两倍于一夸脱瓶装的番茄酱”，因此得出结论说，番茄酱市场是完全有效市场。

　　但是，无论是如此辛辣的讽刺，还是耶鲁大学经济学教授希勒比较客气的批评，都没起什么大作用，金融理论家继续相信，他们的模型基本正确。许多进行现实经济决策的人士也这样相信，其中的强硬派尤以时任美联储主席的格林斯潘为首。他对于放松金融管制向来抱以支持态度。他之所以对人们要求控制次贷的呼声毫不理会，对人们要求他回应日益膨胀的房地产泡沫的声讨充耳不闻，其中很大部分原因在于他始终相信现代金融经济学已经可以掌控一切。2005年，在一个为表彰格林斯潘长期任职于美联储而举行的会议上，有一个令人难忘的时刻：一位出身芝加哥大学的勇敢的与会者当场出示一篇论文警告说，当前金融体系所担的风险水平已经具有潜在危险。这一举动无疑遭到了在场所有人的哂笑，其中当然包括美联储主席萨默斯，当时的他也将这个突如其来的警告当作是“被误导”的言论而拒绝考虑。

　　终于在去年10月，事情发生了戏剧性的变化。格林斯潘承认说，当金融海啸发生的时候，他正处于“极度震惊，甚至难以置信”的状态中，灾难的发生对他而言意味着“整个理智大厦”的崩溃。更可怕的是，理智大厦崩溃的同时也是真实世界里市场经济的崩溃，直接后果是不能想象的经济衰退。无论是从哪个层面考量，这都是自经济大萧条以来美国经历的最为严重的一次经济衰退。面对这样的窘境，决策者该怎么做？很不幸，宏观经济学爱莫能助，因为本应对经济衰退提供明确指导的宏观经济学本身已陷入一片混乱。

　　(作者系纽约时报专栏作家、2008年度诺贝尔经济学奖得主)
【原載2009年09月17日<时代周报>，译者﹕朱兀尘、关晓蕾、单丽霞】
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How Did Economists Get It So Wrong?
(New York Times,9-7-2009)
By PAUL KRUGMAN

I. MISTAKING BEAUTY FOR TRUTH

It’s hard to believe now, but not long ago economists were congratulating themselves over the success of their field. Those successes — or so they believed — were both theoretical and practical, leading to a golden era for the profession. On the theoretical side, they thought that they had resolved their internal disputes. Thus, in a 2008 paper titled “The State of Macro” (that is, macroeconomics, the study of big-picture issues like recessions), Olivier Blanchard of M.I.T., now the chief economist at the International Monetary Fund, declared that “the state of macro is good.” The battles of yesteryear, he said, were over, and there had been a “broad convergence of vision.” And in the real world, economists believed they had things under control: the “central problem of depression-prevention has been solved,” declared Robert Lucas of the University of Chicago in his 2003 presidential address to the American Economic Association. In 2004, Ben Bernanke, a former Princeton professor who is now the chairman of the Federal Reserve Board, celebrated the Great Moderation in economic performance over the previous two decades, which he attributed in part to improved economic policy making.

Last year, everything came apart.

Few economists saw our current crisis coming, but this predictive failure was the least of the field’s problems. More important was the profession’s blindness to the very possibility of catastrophic failures in a market economy. During the golden years, financial economists came to believe that markets were inherently stable — indeed, that stocks and other assets were always priced just right. There was nothing in the prevailing models suggesting the possibility of the kind of collapse that happened last year. Meanwhile, macroeconomists were divided in their views. But the main division was between those who insisted that free-market economies never go astray and those who believed that economies may stray now and then but that any major deviations from the path of prosperity could and would be corrected by the all-powerful Fed. Neither side was prepared to cope with an economy that went off the rails despite the Fed’s best efforts.

And in the wake of the crisis, the fault lines in the economics profession have yawned wider than ever. Lucas says the Obama administration’s stimulus plans are “schlock economics,” and his Chicago colleague John Cochrane says they’re based on discredited “fairy tales.” In response, Brad DeLong of the University of California, Berkeley, writes of the “intellectual collapse” of the Chicago School, and I myself have written that comments from Chicago economists are the product of a Dark Age of macroeconomics in which hard-won knowledge has been forgotten.

What happened to the economics profession? And where does it go from here?

As I see it, the economics profession went astray because economists, as a group, mistook beauty, clad in impressive-looking mathematics, for truth. Until the Great Depression, most economists clung to a vision of capitalism as a perfect or nearly perfect system. That vision wasn’t sustainable in the face of mass unemployment, but as memories of the Depression faded, economists fell back in love with the old, idealized vision of an economy in which rational individuals interact in perfect markets, this time gussied up with fancy equations. The renewed romance with the idealized market was, to be sure, partly a response to shifting political winds, partly a response to financial incentives. But while sabbaticals at the Hoover Institution and job opportunities on Wall Street are nothing to sneeze at, the central cause of the profession’s failure was the desire for an all-encompassing, intellectually elegant approach that also gave economists a chance to show off their mathematical prowess.

Unfortunately, this romanticized and sanitized vision of the economy led most economists to ignore all the things that can go wrong. They turned a blind eye to the limitations of human rationality that often lead to bubbles and busts; to the problems of institutions that run amok; to the imperfections of markets — especially financial markets — that can cause the economy’s operating system to undergo sudden, unpredictable crashes; and to the dangers created when regulators don’t believe in regulation.

It’s much harder to say where the economics profession goes from here. But what’s almost certain is that economists will have to learn to live with messiness. That is, they will have to acknowledge the importance of irrational and often unpredictable behavior, face up to the often idiosyncratic imperfections of markets and accept that an elegant economic “theory of everything” is a long way off. In practical terms, this will translate into more cautious policy advice — and a reduced willingness to dismantle economic safeguards in the faith that markets will solve all problems.

II. FROM SMITH TO KEYNES AND BACK

The birth of economics as a discipline is usually credited to Adam Smith, who published “The Wealth of Nations” in 1776. Over the next 160 years an extensive body of economic theory was developed, whose central message was: Trust the market. Yes, economists admitted that there were cases in which markets might fail, of which the most important was the case of “externalities” — costs that people impose on others without paying the price, like traffic congestion or pollution. But the basic presumption of “neoclassical” economics (named after the late-19th-century theorists who elaborated on the concepts of their “classical” predecessors) was that we should have faith in the market system.

This faith was, however, shattered by the Great Depression. Actually, even in the face of total collapse some economists insisted that whatever happens in a market economy must be right: “Depressions are not simply evils,” declared Joseph Schumpeter in 1934 — 1934! They are, he added, “forms of something which has to be done.” But many, and eventually most, economists turned to the insights of John Maynard Keynes for both an explanation of what had happened and a solution to future depressions.

Keynes did not, despite what you may have heard, want the government to run the economy. He described his analysis in his 1936 masterwork, “The General Theory of Employment, Interest and Money,” as “moderately conservative in its implicati xWww Mortgagedealslending Tag South Mortgage Deals Lending 戴开元博客: 克鲁格曼：为什么经济学家如此不靠谱o Lending Mortgage hWww Mortgagedealslending Tag South Mortgage Deals Lending 戴开元博客: 克鲁格曼：为什么经济学家如此不靠谱f i Mortgage Deals Lending Deals