注册 登录  
 加关注
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

保罗·克鲁格曼 中文博客

授权网易博客进行中文翻译并推广

 
 
 

日志

 
 
关于我

美国经济学家

2008年诺贝尔经济学奖得主。 美國經濟學家及紐約時報的專欄作家,普林斯頓大學經濟系教授,是新凱恩斯主義经济学派代表。1953年出生美國紐約,约翰·F·肯尼迪高中毕业。1974年就讀耶鲁大學,1977年在麻省理工學院取得博士學位,受到经济学家诺德豪斯的注意。畢業後先後於耶鲁大学、麻省理工及史丹福大學任教。2000年起,成為普林斯頓大學經濟系教授。

文章分类
网易考拉推荐

为郁闷的科学而鸣  

2009-08-15 22:39:41|  分类: 默认分类 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

In defence of the dismal science

by Robert Lucas

Eugene Chen [译]


In a guest article, Robert Lucas, the John Dewey Distinguished Service Professor of Economics at the University of Chicago, rebuts criticisms that the financial crisis represents a failure of economics 

为捍卫郁闷的科学而鸣

罗伯特卢卡斯是芝加哥大学经济系的“约翰杜威卓越服务”讲席教授。 在这篇特邀文章里, 他驳斥了金融危机就代表经济学失败的批评。  

THERE is widespread disappointment with economists now because we did not forecast or prevent the financial crisis of 2008. The Economist’s articles of July 18th on the state of economics were an interesting attempt to take stock of two fields, macroeconomics and financial economics, but both pieces were dominated by the views of people who have seized on the crisis as an opportunity to restate criticisms they had voiced long before 2008. Macroeconomists in particular were caricatured as a lost generation educated in the use of valueless, even harmful, mathematical models, an education that made them incapable of conducting sensible economic policy. I think this caricature is nonsense and of no value in thinking about the larger questions: What can the public reasonably expect of specialists in these areas, and how well has it been served by them in the current crisis? 

时下,到处弥漫着一片对经济学失望的情绪, 原因是我们对2008年发生的金融危机,既没有预测准,也无法躲得开。七月十八日那期的经济学人登载了两篇有关经济学现状的文章,就是试图对宏观经济学和金融经济学这两个领域做一次盘点摸底;不过,支配那两篇东西的观点,都是来自这样一伙人,他们这回逮住了金融危机不放,再一次重弹自己远在2008年之前很早就一直提出的批评老调。尤其是宏观经济学家们, 被丑化为迷失的一代, 说他们所受的教育就是学会使用一些不但毫无价值、甚至有害无益的数学模型;这种教育,使他们失去执行明智的经济政策之能力。如此的丑化, 我觉得既是荒唐, 也对考虑如下这些更重大的问题没有助益:那就是, 在这两个领域里, 公众对专家可以合理地期望得到什么?在本次危机中, 专家对公众的服务究竟好坏如何? 

One thing we are not going to have, now or ever, is a set of models that forecasts sudden falls in the value of financial assets, like the declines that followed the failure of Lehman Brothers in September. This is nothing new. It has been known for more than 40 years and is one of the main implications of Eugene Fama’s “efficient-market hypothesis” (EMH), which states that the price of a financial asset reflects all relevant, generally available information. If an economist had a formula that could reliably forecast crises a week in advance, say, then that formula would become part of generally available information and prices would fall a week earlier. (The term “efficient” as used here means that individuals use information in their own private interest. It has nothing to do with socially desirable pricing; people often confuse the two.) 

有一样东西, 我们不但今天拿不到, 将来也永远别想拿到, 那就是这样一组模型, 可用来预测金融资产价值的突然下跌, 就像九月份李曼兄弟倒闭之后股市的大掉价那样。这样说可不是什么标新立异,四十多年前早就知道。 这乃是尤金法玛的“有效市场假说”(EMH) 的几个主要涵义之一。 这个假说讲的就是任一金融资产的价格都已经反映了一切有关的、广泛可获的信息。假如有个经济学家发明了一个公式能够, 比如说, 提前一周, 可靠地预测危机的发生,那么, 这个公式也会变成广泛可获的信息之一部,从而价格也会提前一周就下降。 (“有效市场假说”中的有效二字, 用在这个场合, 意思就是, 每个人都在利用信息以谋私利。 这跟从社会观点看的最佳定价毫无关系;人们却常常将这两者混淆起来。) 

Mr Fama arrived at the EMH through some simple theoretical examples. This simplicity was criticised in The Economist’s briefing, as though the EMH applied only to these hypothetical cases. But Mr Fama tested the predictions of the EMH on the behaviour of actual prices. These tests could have come out either way, but they came out very favourably. His empirical work was novel and carefully executed. It has been thoroughly challenged by a flood of criticism which has served mainly to confirm the accuracy of the hypothesis. Over the years exceptions and “anomalies” have been discovered (even tiny departures are interesting if you are managing enough money) but for the purposes of macroeconomic analysis and forecasting these departures are too small to matter. The main lesson we should take away from the EMH for policymaking purposes is the futility of trying to deal with crises and recessions by finding central bankers and regulators who can identify and puncture bubbles. If these people exist, we will not be able to afford them. 

法玛获得EMH是通过对几个简单理论实例的研究。 经济学人的那篇简报对个中的简单性却加以鞑伐, 好像EMH只能适用于这些假想性的案例。 殊不知法玛早已经检验了EMH对实际价格行为的预测。这些检验,检出的东西原本是无可无不可的, 但是,结果却发现,大大有利于EMH。他所做的实证工作, 既新颖, 又搞得很细致。 而且, EMH还对付过各色各样潮水般批评的充分挑战; 到头来, 这些挑战大部分却都反过来证实EMH的精确性。在过去的年间里,我们是发现过例外和“异常”的情形的(如果你正在管理一笔足够多的钱, 即使实际情形与EMH只有小小的偏离, 也会引人兴趣),不过, 就宏观经济学分析和预测的目的而言,这些偏离太小了,不起作用。从制定政策的目的出发, 我们应从EMH学到的主要教训是:靠寻找能够鉴别泡沫并能刺破泡沫的中央银行家以及调控家来对付危机和衰退,必定无功而返。 就算是世上真有这样的奇才怪杰,我们也雇不起。  

The Economist’s briefing also cited as an example of macroeconomic failure the “reassuring”  simulations that Frederic Mishkin, then a governor of the Federal Reserve, presented in the summer of 2007. The charge is that the Fed’s FRB/US forecasting model failed to predict the events of September 2008. Yet the simulations were not presented as assurance that no crisis would occur, but as a forecast of what could be expected conditional on a crisis not occurring. Until the Lehman failure the recession was pretty typical of the modest downturns of the post-war period. There was a recession under way, led by the decline in housing construction. Mr Mishkin’s forecast was a reasonable estimate of what would have followed if the housing decline had continued to be the only or the main factor involved in the economic downturn. After the Lehman bankruptcy, too, models very like the one Mr Mishkin had used, combined with new information, gave what turned out to be very accurate estimates of the private-spending reductions that ensued over the next two quarters. When Ben Bernanke, the chairman of the Fed, warned Hank Paulson, the then treasury secretary, of the economic danger facing America immediately after Lehman’s failure, he knew what he was talking about. 

经济学人的那篇简报还引用了时为联储会委员的米什金在2007年提交的一个旨在“安定军心”的模拟结果,并将之视为宏观经济学失败的一个实例。其所安之罪名是联储会的“联储银行/美国”预测模型未能预测到2008年九月份的事件。可是,当时提交这个模拟结果, 目的并不是作为定心丸, 保证不会发生危机, 而是当作一个条件预测, 看看在不发生危机的条件下, 我们可以期望些什么。  直到李曼兄弟倒闭之前, 当时的衰退仍然是一直呈现着战后经济周期温和下降的典型特征。那时,一场由房屋开工率减少领头的衰退 正在进行。米什金的模型预测,合理地估计了,在房屋开工率减少持续作为经济下降期的唯一或主要因素的条件下,都会发生些什么。 李曼破产后, 其他非常类似米什金所用的模型, 整合了新的信息,对其后两个季度私人开支的减少,也给出相当精确的估计。当联准会主席伯南克, 警告当时的财长鲍尔逊,美国在李曼破产后将立即面临一场经济危机时,他可不是信口开河的啊。  

Mr Mishkin recognised the potential for a financial crisis in 2007, of course. Mr Bernanke certainly did as well. But recommending pre-emptive monetary policies on the scale of the policies that were applied later on would have been like turning abruptly off the road because of the potential for someone suddenly to swerve head-on into your lane. The best and only realistic thing you can do in this context is to keep your eyes open and hope for the best. 

当然啰,米什金早在2007年就已认识到发生金融危机的潜在可能性。伯南克肯定也是的。 但是, 如果那时就推荐及早抢先地施行货币政策,并以后来实际采用政策时的大规模来施行之, 这就好像是因为担心别人有潜在的可能会突然从对面转进自己的车道,迎面撞来,而索性把车猛地开离道路一样。 在这种情况下, 唯一现实的、也是最好的办法就是保持自己耳聪目明, 并希望自己的命运是上上签。  

After Lehman collapsed and the potential for crisis had become a reality, the situation was completely altered. The interest on Treasury bills was close to zero, and those who viewed interest-rate reductions as the only stimulus available to the Fed thought that monetary policy was now exhausted. But Mr Bernanke immediately switched gears, began pumping cash into the banking system, and convinced the Treasury to do the same. Commercial-bank reserves grew from $50 billion at the time of the Lehman failure to something like $800 billion by the end of the year. The injection of Troubled Asset Relief Programme funds added more money to the financial system. 

李曼垮台之后, 危机的潜在可能性已随之转成现实性, 这时, 形势完全变了个模样。 短期国库券的利率已经接近零, 那些将减息视为联准会刺激经济可用的唯一工具的人, 都觉得货币政策已是强弩之末。 不料伯南克立马改弦更张, 开始将现金挹注进银行系统,并说服财政部依葫芦画瓢。 商业银行的储备金从李曼垮台时的500亿增到年底时的8000亿。 “麻烦资产救济方案”基金的挹注也增加了金融系统的货币数量。  

There is understandable controversy about many aspects of these actions but they had the great advantages of speed and reversibility. My own view, as expressed elsewhere, is that these policies were central to relieving a fear-driven rush to liquidity and so alleviating (if only partially) the perceived need for consumers and businesses to reduce spending. The recession is now under control and no responsible forecasters see anything remotely like the 1929-33 contraction in America on the horizon. This outcome did not have to happen, but it did. 

这些举措的许多方面不免有可争议之处,这点还是可以理解的。 但是, 凡如此举措都有一大优点, 那就是速效性加上可逆性。 我自己的看法, 亦见于别处,  就是:这些政策的实施, 对纾解因恐惧驱使而挤兑现金之狂潮,对降低(即使是部分降低)顾客和企业所主观感受的节约开支的需要, 都有着核心的重要性。 经济衰退, 现已在可控范围之内。 凡是有责任心的预测家, 没有人会说美国会在不久的将来出现能与1929-33大萧条差堪相比的事情。这个(好)结果不是必然就会发生的, 但是它的确发生了。   

Not bad for a Dark Age 

Both Mr Bernanke and Mr Mishkin are in the mainstream of what one critic cited in The Economist’s briefing calls a “Dark Age of macroeconomics”. They are exponents and creative builders of dynamic models and have taught these “spectacularly useless” tools, directly and through textbooks that have become industry standards, to generations of students. Over the past two years they (and many other accomplished macroeconomists) have been centrally involved in responding to the most difficult American economic crisis since the 1930s. They have forecasted what can be forecast and formulated contingency plans ready for use when unforeseeable shocks occurred. They and their colleagues have drawn on recently developed theoretical models when they judged them to have something to contribute. They have drawn on the ideas and research of Keynes from the 1930s, of Friedman and Schwartz in the 1960s, and of many others. I simply see no connection between the reality of the macroeconomics that these people represent and the caricature provided by the critics whose views dominated The Economist’s briefing. 

对黑暗世纪来说,可算不错了 

伯南克和米什金都可算是经济学人那篇简报所援引的一位批评家称之为“宏观经济学黑暗世纪”里的两个主流的经济学家。 他们都是动态模型的倡导者, 也是动态模型的有创意的建造者。他们都曾对几代的学生们传授过这些“无用到惊世骇俗地步”的工具, 要么直接地面授机宜, 要么通过已成为行业规范的教科书。  过去两年间, 他们(以及其他许多学有所成的宏观经济学家们) 都关键性地参予了回应自1930年代以来美国所发生的最大经济危机的活动。 能够给予预测的他们都做了预测。 他们也都参予制定应急计划, 可在发生不可预知的扰动时立马投入使用。 他们和自己的同事对晚近发展的理论模型一旦判断有新贡献之处,都加以汲取。  他们也从1930年代的凯恩斯、1960年代的佛里德曼和施瓦慈,还有其他许多人的理念和研究中汲取养分。 在这些人所代表的宏观经济学的现实图画与支配经济学人那篇简报的批评家所提供的丑化性漫画两者之间, 我实在看不出有什么联系。

编辑手记:

* Eugene的来信中说道:

This article of Lucas's is in fact a response to Krugman's comment of the Dark Age status of current macroeconomics.
 
I have posted it on the common area of zou's blog.
 
I would also like to see it posted on your Krugman's Chinese blog, if doing so is not in conflict with your blog policy.

*  因为网易的标题显示为"八个字",所以,我修改了一下标题.
  评论这张
 
阅读(9780)| 评论(76)
推荐 转载

历史上的今天

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2017