The last temptation of risk.

• Author: Eichengreen, Barry
• Position: United States financial crises

The Great Credit Crisis has cast into doubt much of what we thought we new about economics. We thought that monetary policy had tamed the business cycle. We thought that because changes in central-bank policies had delivered low and stable inflation, the volatility of the pre-1985 years had been consigned to the dustbin of history; they had given way to the quaintly dubbed "Great Moderation." We thought that financial institutions and markets had come to be self-regulating--that investors could be left largely if not wholly to their own devices. Above all we thought that we had learned how to prevent the kind of financial calamity that struck the world in 1929.

We now know that much of what we thought was true was not. The Great Moderation was an illusion. Monetary policies focusing on low inflation to the exclusion of other considerations (not least excesses in financial markets) can allow dangerous vulnerabilities to build up. Relying on institutional investors to self-regulate is the economic equivalent of letting children decide their own diets. As a result we are now in for an economic and financial downturn that will rival the Great Depression before it is over.

The question is how we could have been so misguided. One interpretation, understandably popular given our current plight, is that the basic economic theory informing the actions of central bankers and regulators was fatally flawed. The only course left is to throw it out and start over. But another view, considerably closer to the truth, is that the problem lay not so much with the poverty of the underlying theory as with selective reading of it--a selective reading shaped by the social milieu. That social milieu encouraged financial decision makers to cherry-pick the theories that supported excessive risk taking. It discouraged whistle-blowing, not just by risk-management officers in large financial institutions, but also by the economists whose scholarship provided intellectual justification for the financial institutions' decisions. The consequence was that scholarship that warned of potential disaster was ignored. And the result was global economic calamity on a scale not seen for four generations.

So where were the intellectual agenda setters when the crisis was building? Why did they fail to see this train wreck coming? More than that, why did they consort actively with the financial sector in setting the stage for the collapse?

For economists in business schools the answer is straightforward. Business schools see themselves as suppliers of inputs to business. Just as General Motors provides its suppliers with specifications for the cold-rolled sheet it needs for fabricating auto bodies, J. P. Morgan makes clear the kind of financial engineers it requires, and business schools deem to provide. In the wake of the 1987 stock-market crash, Morgan's chairman, Dennis Weatherstone, started calling for a daily "4:15 Report" summarizing how much his firm would lose if tomorrow turned out to be a bad day. His counterparts at other firms then adopted the practice. Soon after, business schools jumped to supply graduates to write those reports. Value at Risk, as that number and the process for calculating it came to be known, quickly gained a place in the business-school curriculum.

The desire for up-to-date information on the risks of doing business was admirable. Less admirable was the belief that those risks could be reduced to a single number which could then be estimated on the basis of a set of mathematical equations fitted to a few data points. Much as former-GM CEO Alfred Sloan once sought to transform automobile production from a craft to an engineering problem, Weatherstone and his colleagues encouraged the belief that risk and return could be reduced to a set of equations specified by an MBA and solved by a machine.

Getting the machine to spit out a headline number for Value at Risk was straightforward. But deciding what to put into the model was another matter. The art of gauging Value at Risk required imagining the severity of the shocks to which the portfolio might be subjected. It required knowing what new variables to add in response to financial innovation and unfolding events. Doing this right required a thoughtful and creative practitioner. Value at Risk, like dynamite, can be a powerful tool when in the right hands. Placed in the wrong hands--well, you know.

These simple models should have been regarded as no more than starting points for serious thinking. Instead, those responsible for making key decisions, institutional investors and their regulators alike, took them...