Alan Greenspan has just testified before the House Oversight and Government Reform Committee. From his prepared remarks (PDF) are these comments on the role of risk models and ratings agencies in the financial crisis:

What went wrong with global economic policies that had worked so effectively for nearly four decades? The breakdown has been most apparent in the securitization of home mortgages. The evidence strongly suggests that without the excess demand from securitizers, subprime mortgage originations (undeniably the original source of crisis) would have been far smaller and defaults accordingly far fewer. But subprime mortgages pooled and sold as securities became subject to explosive demand from investors around the world. These mortgage backed securities being “subprime” were originally offered at what appeared to be exceptionally high risk-adjusted market interest rates. But with U.S. home prices still rising, delinquency and foreclosure rates were deceptively modest. Losses were minimal. To the most sophisticated investors in the world, they were wrongly viewed as a “steal.”

The consequent surge in global demand for U.S. subprime securities by banks, hedge, and pension funds supported by unrealistically positive rating designations by credit agencies was, in my judgment, the core of the problem. Demand became so aggressive that too many securitizers and lenders believed they were able to create and sell mortgage backed securities so quickly that they never put their shareholders’ capital at risk and hence did not have the incentive to evaluate the credit quality of what they were selling. Pressures on lenders to supply more “paper” collapsed subprime underwriting standards from 2005 forward. Uncritical acceptance of credit ratings by purchasers of these toxic assets has led to huge losses.

It was the failure to properly price such risky assets that precipitated the crisis. In recent decades, a vast risk management and pricing system has evolved, combining the best insights of mathematicians and finance experts supported by major advances in computer and communications technology. A Nobel Prize was awarded for the discovery of the pricing model that underpins much of the advance in derivates markets. This modern risk management paradigm held sway for decades. The whole intellectual edifice, however, collapsed in the summer of last year because the data inputted into the risk management models generally covered only the past two decades, a period of euphoria. Had instead the models been fitted more appropriately to historic periods of stress, capital requirements would have been much higher and the financial world would be in far better shape today, in my judgment.

When in August 2007 markets eventually trashed the credit agencies’ rosy ratings, a blanket of uncertainty descended on the investment community. Doubt was indiscriminately cast on the pricing of securities that had any taint of subprime backing. As much as I would prefer it otherwise, in this financial environment I see no choice but to require that all securitizers retain a meaningful part of the securities they issue. This will offset in part market deficiencies stemming from the failures of counterparty surveillance.