個人資料
正文

Joseph Stiglitz 北大西洋危機給經濟學理論和政策帶來的教訓

(2024-05-28 11:46:15) 下一個

北大西洋危機給經濟學理論和政策帶來的教訓

作者:約瑟夫 • 斯蒂格利茨 2013年5月3日

iMFdirect blog home: http://blog-imfdirect.imf.org/

紐約哥倫比亞大學教授,宏觀政策再思考 II:最初的舉措和早期教訓會議的共同主持人
在分析最近的金融危機時,我們多少可以從近幾十年的遭遇中獲得某些助益。近三十
年來(期間放開政策成為主導)共發生了大約一百次危機,它們為我們提供了豐富的
經驗和大量的數據。如果將分析區間擴大到 150 年,則數據更加豐富。

一個半世紀以來一次接一次的危機所提供的詳細信息提出了一個急需回答的問題。但
是,這個問題不是“危機是如何發生的?”而是“我們怎麽會忽視那麽漫長的曆史,
以為已經解決了商業周期問題?”認為嚴重的經濟波動已成為過去是這種狂妄自大背
後的主要原因。

市場不穩定、不有效,也不是自我矯正的

此次危機令我們猛醒的一個巨大的教訓(我們早就應該明白這一點)是,經濟體不一
定是有效、穩定和自我矯正的。

這一遲來的覺醒由兩部分組成。其一是注重外生衝擊的標準模型。很明顯,我們經濟
問題的很大一部分是內生的。不僅有短期的內生衝擊,也有長期的結構性轉型以及持
續性的衝擊。那些注重外生衝擊的模型誤導了我們,大部分非常大的衝擊都源自於經
濟體內部。

其二,經濟體不能自我矯正。很明顯,我們還沒有吃透從這次危機中得到的關鍵教訓,
即使在危機過後,歐美各國縮手縮腳的修複經濟的努力都失敗了。各國顯然做得不夠。
其結果是,我們繼續麵臨未來再度發生危機的重大風險。

此外,回應危機的努力遠未使各國經濟體回到充分就業狀態。潛在和實際 GDP 之間的
差距有幾萬億美元之巨。

當然,有些人會說結果可能會更糟,這話不錯。那些負責解決危機的人中,有些人原
本就是危機的製造者。從這個角度來看,沒有發生更大的災難也許還是一件了不起的
事情。

比去杠杆化和資產負債表危機更重要的是:必須進行結構轉型

從人力資源、資本儲備和自然資源來看,我們今天基本處於危機前的水平。與此同時,
許多國家的 GDP 尚未恢複到危機前的水平,更不要說回到危機前的增長路徑。從根本
意義上來說,危機尚未得到全麵的解決,沒有一種好的經濟理論能夠解釋為什麽會這
樣。

其中部分原因在於去杠杆化進程緩慢。但是,即使經濟在降低杠杆率,完全有理由相
信不會回複充分就業。我們不太可能回到危機前家庭儲蓄率為零的狀態,真的發生這
種情況也不是好事。即使製造業稍許複蘇,這一部門已經失去的就業機會也不會失而
複得。

有些人認為,從以往數據來看,我們對這種不幸的狀況無能為力。經曆嚴重金融危機
的經濟體一般複蘇緩慢。但是,雖然金融危機之後往往會出問題並不意味著一定會出
問題。

這不僅僅是資產負債表危機。一個更加深層的原因是:歐美各國正經曆著一場結構性
的轉型。與這一結構型轉型相關聯的是從製造業經濟向服務業經濟的轉變。此外,比
較優勢的變化要求北大西洋國家的結構發生重大調整。

改革充其量隻觸及了皮毛

市場自身一般不會帶來有效、穩定和為社會所接受的結果。這意味著,我們必須更加
深刻地思考:什麽樣的經濟結構能夠帶來增長、真正的穩定以及良好的收入分配。
目前一直在進行的辯論是,我們應該隻是對現有的經濟結構進行微調,還是必須進行
根本性的改革。我有兩項擔憂。一項是先前已經暗示過的:迄今為止的改革隻觸及皮
毛。其次是,(危機前後)進行的一些意在改善經濟表現的改革可能並未取得成功。
比方說,有些改革可能使得經濟能夠更好地抵禦小衝擊,但是實際上卻使得經濟承受
大衝擊的能力降低。金融部門的許多整合都是這樣,雖然使得經濟能夠承受一些較小
的衝擊,但顯然使得經濟抵禦更大的肥尾衝擊的能力下降。

很清楚,危機前市場的許多“改善”實際上增加了各國的風險敞口。資本和金融市場
放開可能帶來的任何(可疑的)好處,都具有增加風險的巨大成本。我們必須重新思
考對這類改革的態度,基金組織近年來的反思值得稱讚。各種形式的資本賬戶管理的
目標之一,是降低一個國家因國際交往而產生的國內波動性。

更廣義而言,這場危機使得人們認識到保持宏觀穩定的金融監管的重要性。但是我在
評估危機後事件時感到失望。危機後發生的兼並使得銀行大到不能倒的問題更加嚴重。
但是,問題不僅在於那些大到不能倒的銀行。有些銀行因彼此盤根錯節而不能倒,有
些銀行則是因相互關聯而不能倒。我們在這方麵無所作為。當然,對大到不能倒的問
題已經展開了大量的討論。但是,過度關聯是一個獨特的問題。金融機構的生態很有

必要多樣化,降低過度關聯的衝動,從而增加穩定性。這種觀點還遠未得到足夠的重
視。

此外,我們在增加銀行資本要求方麵做得也不夠。大量討論都缺乏對於提高資本要求
的成本和益處的評估。我們知道其益處——降低需要政府救助以及 2007 年和 2008 年
事件複發的風險。但在成本方麵,我們對於 Modigliani-Miller 定理的根本性洞見不夠重
視,這項定理解釋了為什麽所謂增加資本要求將提高資本成本的說法是謬論。

改革和模型存在的缺陷

如果我們在改革之初將重點放在如何使經濟更加有效和穩定,那麽我們自然會提出另
外一些問題。有趣的是,在改革的缺陷與經濟學家們經常運用的宏觀經濟學模型缺陷
之間存在某種相關性。

信用的重要性

例如,我們會問金融部門的根本作用是什麽,以及如何使之更好地發揮這些作用。顯
然,這些關鍵的作用之一是資本配置和提供信用,尤其是向中小型企業提供信用。金
融部門在危機前沒有很好地發揮這一功能,而且可以說至今任然沒有做好。

這一點似乎很明顯。無論是政策文件還是標準宏觀模型,都沒有注重信用的提供。我
們必須將重點從資金轉向信用。任何資產負債表的兩邊通常都是高度關聯的,但現實
並非總是如此,尤其在出現大幅經濟動蕩時。在這種時刻,我們必須將重點放在信用
上。標準宏觀模型對於信用機製的本質缺乏適當研究,其缺乏程度非同尋常。當然,
關於銀行業務與信用的微觀經濟學文獻汗牛充棟,但總的來說,這些文獻中的見解並
未納入標準宏觀經濟模型。

但是,我們做法的缺陷不僅在於管理信用,還在於對不同融資類型缺乏理解。在分析
金融市場風險中,一個重要的方麵是債務與股權的區別。在標準宏觀經濟學當中,我
們很少關注這個問題。我與 Bruce Greenwald 合著的《論貨幣經濟學新範式》(劍橋大
學出版社 2003 年版)一書試圖彌補這一不足。

穩定

如上所述,根據常規模型(以及常識),市場經濟是穩定的。因此,毫不奇怪,人們
很少問應該如何設計更加穩定的經濟體係。我們已經談到了幾個方麵:如何設計風險
較小或自身波動性較小的經濟體係。

一個有必要但沒有得到足夠重視的改革是,必須建立更多的自動穩定器,減少自動失
穩器。不僅在金融部門,而且在整個經濟當中都要這樣。比如說,從固定福利體係向
固定繳款體係過渡可能使得經濟更加不穩定。

我在別處曾經解釋過,風險分擔安排(尤其是設計欠佳時)實際上可能增加係統性風
險:危機前一般認為多樣化基本上消除了風險的看法是錯誤的。我在這篇文章、此篇
論文和本篇文章中對此做了詳細的分析。

分布

分布也是重要的—在個人、家庭和企業之間、家庭之間以及企業當中的分布。傳統上
講,宏觀經濟學注重某些總量,如杠杆與 GDP 的平均比率。但是,這一數字和其他平
均數字往往不能展示一個經濟體的脆弱性。

在本次金融危機中,這些數字沒有提供預警信號。實際上,大量底層人群無法按期償
債這一事實,原本應該讓我們發覺出了問題。

我們所有的模型都有必要具備一種對於異質性及其對經濟穩定的啟示的理解。

政策框架

有缺陷的模型不僅導致錯誤的政策,而且也導致錯誤的政策框架。

貨幣政策應該僅僅注重短期利率嗎?

在貨幣政策中,人們傾向於認為,央行隻能通過設定短期利率進行幹預。他們認為,
“單項幹預”優於多項幹預。自從八十年以前 Ramsey 的工作發表以來,我們知道集中
於一項工具一般說來不是最好的方法。

主張“單一幹預”的人認為這是最佳的方法,因為它對於經濟的扭曲最小。當然,我
們之所以有貨幣政策(也就是政府為什麽幹預經濟的原因),就是因為我們不相信市
場自身能夠設定正確的短期利率。如果我們相信的話,就會讓自由市場來決定利率了。
一件奇怪的事是,雖然幾乎每家央行都會同意應該幹預利率的定價,卻不是所有人都
相信我們應該對其他事情進行戰略性幹預,盡管有關稅收和市場幹預的一般理論告訴
我們,僅僅幹預一種價格並不是最優的做法。

一旦我們將分析的重點轉移到信用,並明確地將風險納入分析之中,我們就認識到有
必要運用多種工具。事實上,我們應該運用所有可支配的工具。貨幣經濟學家往往在
宏觀審慎、微觀審慎和常規貨幣政策工具之間加以分界。我和 Bruce Greenwald 在合著
的《論貨幣經濟學新範式》一書中認為,這一分界是人為的。政府應該以協調的方式,
調動所有工具(我回頭再來討論這個問題)。

當然,我們不可能“糾正”每一次市場失靈。但是,我們必須總是幹預那些很大的宏
觀經濟失靈。Bruce Greenwald 和我指出,如果存在信息不完美或不對稱,或風險市場
不完美,那麽市場效率就永遠不會是帕累托最優。因為這些狀態永遠存在,市場效率
永遠不會達到帕累托最優。最近的研究昭示了這些以及其他相關製約因素對於宏觀經濟的重要性,不過,這些重要研究工作的洞見還沒有被適當地納入主流宏觀經濟模型
或宏觀經濟政策的討論中去。

是價格,還是量化幹預

這些理論上的洞見也有助於我們理解,為什麽一些經濟學家關於價格幹預優於量化幹
預的陳舊假設是錯誤的。在很多情況下,量化幹預帶來更好的經濟表現。

廷伯根

在某些範圍內變得比較流行的一種政策框架認為,隻要工具和目標的數量匹配,經濟
體係就是可控的,在這種情況下,管理經濟的最佳方法是由一個機構負責一個目標和
一個工具。(根據這種觀點,央行具備一項工具,即利率,有一個目標,即通貨膨脹。
我們已經解釋了為什麽將貨幣政策局限於一項工具是錯誤的。)

作這樣的劃分從一個機構或官僚機構的角度來看是有利的,但從管理宏觀經濟政策
(在充滿不確定性的世界中注重增長、穩定和分配)的角度來講,這種劃分毫無道理。
必須在各項問題之間進行協調,並且協調所有的可支配工具。貨幣政策和財政政策之
間必須密切協調。當不同人控製不同工具並著重不同目標時,所產生的自然均衡,一
般來說遠遠不是實現社會整體目標的最優狀態。改善協調以及工具的運用則能夠加強
經濟的穩定。

抓住機遇,改造有缺陷的模型

應該明確的是,我們原本可以更有所作為地防止這次危機的發生並減輕其影響。而且
還應該明確一點,我們應該能夠為避免下一次危機更有所作為。通過這次以及其他類
似的會議,我們至少已經開始明確地指出那些很大的市場失靈,大的宏觀經濟外部性,
以及實現高增長、增強穩定和改善收入分配的更好的政策幹預方式。
要獲得成功,我們必須提醒自己,市場自身不能解決這些問題,僅靠短期利率這樣的
單一幹預也不行。這是過去一個半世紀以來已經被反複證明的事實。
盡管我們麵臨的經濟問題十分嚴峻,認識到這些問題可以使我們利用這一嚴重經濟創
傷時期帶來的重大機遇,即,抓住機遇,改造有缺陷的模型,我們甚至可以走出這一
漫長的危機周期。

The Lessons of the North Atlantic Crisis for Economic Theory and Policy 

Joseph E. Stiglitz  May 3, 2013
 
In analyzing the most recent financial crisis, we can benefit somewhat from the misfortune of recent decades. The approximately 100 crises that have occurred during the last 30 years—as liberalization policies became  dominant—have given us a wealth of experience and mountains of data.  If we look over a 150 year period, we have an even richer data set.

With a century and half of clear, detailed information on crisis after crisis, the burning question is not How did this happen? but How did we ignore that long history, and think that we had solved the problems with the business cycle? Believing that we had made big economic fluctuations a thing of the past took a remarkable amount of hubris.

Markets are not stable, efficient, or self-correcting

The big lesson that  this crisis forcibly brought home—one we should have long known—is that economies are not necessarily efficient, stable or self-correcting.

There are two parts to this belated revelation. One is that standard models had focused on exogenous shocks, and yet it's very clear that a very large fraction of the perturbations to our economy are endogenous.  There are not only short?run endogenous shocks; there are long?run structural transformations and persistent shocks.  The models that focused on exogenous shocks simply misled us—the majority of the really big shocks come from within the economy.

Secondly, economies are not self-correcting.  It’s clear that we have yet to fully take on aboard this crucial lesson that we should have learned from this crisis: even in its aftermath, the tepid attempts to fix the economies of the United States and Europe have been a failure.  They certainly have not gone far enough.  The result is that we continue to face significant risks of another crisis in the future.

So too, the responses to the crisis have not brought our economies anywhere near back to full employment.  The loss in GDP between our potential and our actual output is in the trillions of dollars.

Of course, some will say that it could have been done worse, and that’s true. Considering that the people in charge of fixing the crisis included some of  the same ones who created it in the first place, it is perhaps  remarkable it hasn’t been a bigger catastrophe.

More than deleveraging, more than a balance sheet crisis: the need for structural transformation

In terms of human resources, capital stock, and natural resources, we’re roughly  at the same levels today that we were before the crisis.  Meanwhile, many countries have not regained their pre-crisis GDP levels, to say nothing of a return to the pre-crisis  growth paths. In a very fundamental sense, the crisis is still not fully resolved—and there's no good economic theory that explains why that should be the case.

Some of this has to do with the issue of the slow pace of deleveraging.  But even as the economy deleverages, there is every reason to believe that it will not return to full employment.  We are not likely to return to the pre-crisis household savings rate of zero—nor would it be a good thing if we did.  Even if manufacturing has a slight recovery, most of the jobs that have been lost in that sector will not be regained.

Some have suggested that, looking at past data, we should resign ourselves to this unfortunate state of affairs.  Economies that have had severe financial crises typically recover slowly.  But the fact that things have often gone badly in the aftermath of  a financial crisis doesn't mean they must go badly.

This is more than just a balance sheet crisis.  There is a deeper cause:  The United States and Europe are going through a  structural transformation.  There is a structural transformation associated with the move from manufacturing to a service sector economy.    Additionally, changing comparative advantages requires massive adjustments in the structure of the North Atlantic countries.

Reforms that are, at best, half-way measures

Markets by themselves do not in general lead to efficient, stable and socially acceptable outcomes.  This means we have to think a little bit more deeply about what kind of economic architectures will lead to growth, real stability, and a good distribution of income.

There is an ongoing debate about  whether we simply need to tweak the existing economic architecture or whether we need to make more fundamental changes.  I have two concerns.  One I hinted at earlier:  the reforms undertaken so far have only tinkered at the edges.  The second is that some of the changes in our economic structure (both before and after the crisis) that were supposed to make the economy perform better may not have done so.

There are some reforms, for instance, that may enable the economy to better withstand small shocks, but actually make it less able to absorb big shocks.  This is true of much of the financial sector integration that may have allowed the economy to absorb some of the smaller shocks, but clearly made the economy less resilient to fatter?tail shocks.

It should be clear that many of the "improvements" in markets before the crisis actually increased countries' exposure to risk.  Whatever the benefits that might be derived from capital and financial market liberalization (and they are questionable), there have been severe costs in terms of increased risk.  We ought to be rethinking attitudes towards these reforms—and the IMF should be commended for its rethinking in recent years.  One of the objectives of capital account management, in all of its forms, can be to reduce domestic volatility arising from a country's international engagements.

More generally, the crisis has brought home the importance of financial regulation for macroeconomic stability.  But as I assess what has happened since the crisis, I feel disappointed.  With the mergers that have occurred in the aftermath of the crisis, the problem of too-big-to- fail banks has become even worse.  But the problem is not just with too-big-to-fail banks.  There are banks that are too intertwined to fail and banks that are too correlated to fail.  We have done little about any of these issues. There has, of course, been a huge amount of discussion about too- big-to-fail. But being too correlated is a distinct issue.  There is a strong need for a more diversified ecology of financial institutions that would reduce incentives to be excessively correlated and lead to greater stability.  This is a perspective that has not been emphasized nearly enough.

Also, we haven't done enough to increase bank capital requirements.  Missing in much of the discussion is an assessment of the costs vs. benefits of higher capital requirements.  We know the benefits—a lower risk of a government bailout and a recurrence of the kinds of events that marked 2007 and 2008.  But on the cost side, we’ve paid too little attention to the  fundamental  insights of the Modigliani?Miller Theorem, which explains the bogusness of arguments that increasing capital requirements will increase the cost of capital.

Deficiencies in reforms and in modeling

If we had begun our reform efforts with a focus on how to make our economy more efficient and more stable, there are other questions we would have naturally asked; other questions we would have posed.    Interestingly, there is some correspondence between these deficiencies in our reform efforts and the deficiencies in the models that we as economists often use in macroeconomics.

The importance of credit

We would, for instance, have asked what the fundamental roles of the financial sector are, and how we can get it to perform those roles better.  Clearly, one of the key roles is the allocation of capital and the provision of credit, especially to small and medium-sized enterprises, a function which it did not perform well before the crisis, and which arguably it is still not fulfilling well.

This might seem obvious. But a focus on the provision of credit has neither been at the center of policy discourse nor of the standard macro-models.  We have to shift our focus from money to credit.  In any balance sheet, the two sides are usually going to be very highly correlated.  But that is not always the case, particularly in the context of large economic perturbations.  In these, we ought to be focusing on credit.  I find it remarkable the extent to which there has been an inadequate examination in standard macro models of the nature of the credit mechanism. There is, of course, a large microeconomic literature on banking and credit, but for the most part, the insights of this literature has not been taken on board in standard macro-models.

But failing to manage credit is not the only lacuna in our approach.  There is also a lack of understanding of different kinds of finance.  A major area in the analysis of risk in financial markets is the difference between debt and equity.  And in standard macroeconomics, we have barely given this any attention. My book with Bruce Greenwald, Towards a New Paradigm of Monetary Economics ((Cambridge University Press, 2003) was an attempt to remedy this.

Stability

As I have already noted, in the conventional models (and in the conventional wisdom) market economies were stable.  And so it was perhaps not a surprise that fundamental questions about how to design more stable economic systems were seldom asked.  We have already touched on several aspects of this:  how to design economic systems that are less exposed to risk or that generate less volatility on their own.

One of the necessary reforms, but one not emphasized enough, is the need for more automatic stabilizers and fewer automatic destabilizers—not only in the financial sector, but throughout the economy. For instance, the movement from defined benefit to defined contribution systems may have led to a less stable economy.

Elsewhere, I have explained how risk sharing arrangements (especially if poorly designed) can actually lead to more systemic risk:  the pre-crisis conventional wisdom that diversification essentially eliminates risk is just wrong.  I’ve explored this is some detail in this article, along with this paper and this one.

Distribution

Distribution matters as well—distribution among individuals, between households and firms, among households, and among firms.  Traditionally, macroeconomics focused on certain aggregates, such as the average ratio of leverage to GDP.  But that and other average numbers often don't give a picture of the vulnerability of the economy.

In the case of the financial crisis, such numbers didn’t give us warning signs. Yet it was the fact that a large number of people at the bottom couldn't make their debt payments that should have tipped us off that something was wrong.

Across the board, our models need to incorporate a greater understanding of heterogeneity and its implications for economic stability.

Policy Frameworks

Flawed models not only lead to flawed policies, but also to flawed policy frameworks.

Should monetary policy focus just on short term interest rates? 

In monetary policy, there is a tendency to think that the central bank should only intervene in the setting of the short-term interest rate.  They believe "one intervention" is better than many.  Since at least 80 years ago with the work of Ramsey  we know that focusing on a single instrument is not generally the best approach.

The advocates of the "single intervention" approach argue that it is best, because it least distorts the economy.  Of course, the reason we have monetary policy in the first place—the reason why government acts to intervene in the economy—is that we don't believe that markets on their own will set the right short-term interest rate.  If we did, we would just let free markets determine that interest rate.  The odd thing is that while just about every central banker would agree we should intervene in the determination of that price, not everyone is so convinced that we should strategically intervene in others, even though we know from the general theory of taxation and the general theory of market intervention that intervening in just one price is not optimal.

Once we shift the focus of our analysis to credit, and explicitly introduce risk into the analysis, we become aware that we need to use multiple instruments.  Indeed, in general, we want to use all the instruments at our disposal.  Monetary economists often draw a division between macro-prudential, micro-prudential, and conventional monetary policy instruments.  In our book Towards a New Paradigm in Monetary Economics, Bruce Greenwald and I argue that this distinction is artificial. The government needs to draw upon all of these instruments, in a coordinated way.  (I'll return to this point shortly.)

Of course, we cannot "correct" every market failure. The very large ones, however—the macroeconomic failures—will always require our intervention.  Bruce Greenwald and I have pointed out that markets are never Pareto efficient if information is imperfect, if there are asymmetries of information, or if risk markets are imperfect.  And since these conditions are always satisfied, markets are never Pareto efficient.  Recent research has highlighted the importance of these and other related constraints for macroeconomics—though again, the insights of this important work have yet to be adequately integrated either into mainstream macroeconomic models or into mainstream policy discussions.

Price versus quantitative interventions

These theoretical insights also help us to understand why the old presumption among some economists that price interventions are preferable to quantity interventions is wrong.  There are many circumstances in which quantity interventions lead to better economic performance.

Tinbergen

A policy framework that has become popular in some circles argues that so long as there are as many instruments as there are objectives, the economic system is controllable, and the best way of managing the economy in such circumstances is to have an institution responsible for one target and one instrument.  (In this view, central banks have one instrument—the interest rate—and one objective—inflation.  We have already explained why limiting monetary policy to one instrument is wrong.)

Drawing such a division may have advantages from an agency or bureaucratic perspective, but from the point of view of managing macroeconomic policy—focusing on growth, stability and distribution, in a world of uncertainty—it makes no sense.  There has to be coordination across all the issues and among all the instruments that are at our disposal.  There needs to be close coordination between monetary and fiscal policy.  The natural equilibrium that would arise out of having different people controlling different instruments and focusing on different objectives is, in general, not anywhere near what is optimal in achieving overall societal objectives.  Better coordination—and the use of more instruments—-can, for instance, enhance economic stability.

Take this chance to revolutionize flawed models

It should be clear that we could have done much more to prevent this crisis and to mitigate its effects.   It should be clear too that we can do much more to prevent the next one. Still, through this conference and others like it, we are at least beginning to clearly identify the really big market failures, the big macroeconomic externalities, and the best policy interventions for achieving high growth, greater stability, and a better distribution of income.

To succeed, we must constantly remind ourselves that markets on their own are not going to solve these problems, and neither will a single intervention like short-term interest rates. Those facts have been proven time and again over the last century and a half.

And as daunting as the economic problems we now face are, acknowledging this will allow us to take advantage of the one big opportunity  this period of economic trauma has afforded: namely, the chance to revolutionize our flawed  models, and perhaps even exit from an interminable cycle of crises.

[ 打印 ]
閱讀 ()評論 (0)
評論
目前還沒有任何評論
登錄後才可評論.