The Roots of the Mortgage Crisis by Alan Greenspan

On Aug. 9, 2007, and the days immediately following, financial markets in much of the world seized up. Virtually overnight the seemingly insatiable desire for financial risk came to an abrupt halt as the price of risk unexpectedly surged. Interest rates on a wide range of asset classes, especially interbank lending, asset-backed commercial paper and junk bonds, rose sharply relative to riskless U.S. Treasury securities. Over the past five years, risk had become increasingly underpriced as market euphoria, fostered by an unprecedented global growth rate, gained cumulative traction.

The crisis was thus an accident waiting to happen. If it had not been triggered by the mispricing of securitized subprime mortgages, it would have been produced by eruptions in some other market. As I have noted elsewhere, history has not dealt kindly with protracted periods of low risk premiums.

In addition, there has been a pronounced fall in global real interest rates since the early 1990s, which, of necessity, indicated that global saving intentions chronically had exceeded intentions to invest. In the developing world, consumption evidently could not keep up with the surge of income and, as a consequence, the savings rate of the developed world soared from 24% of nominal GDP in 1999 to 33% in 2006, far outstripping its investment rate.

That weakened global investment has been the major determinant in the decline of global real long-term interest rates is also the conclusion of a recent (March 2007) Bank of Canada study.

Equity premiums and real-estate capitalization rates were inevitably arbitraged lower by the fall in global long-term interest rates. Asset prices accordingly moved dramatically higher. Not only did global share prices recover from the dot-com crash, they moved ever upward.

After more than a half-century observing numerous price bubbles evolve and deflate, I have reluctantly concluded that bubbles cannot be safely defused by monetary policy or other policy initiatives before the speculative fever breaks on its own. There was clearly little the world's central banks could do to temper this most recent surge in human euphoria, in some ways reminiscent of the Dutch Tulip craze of the 17th century and South Sea Bubble of the 18th century.

Arbitragable assets -- equities, bonds and real estate, and the financial assets engendered by their intermediation -- now swamp the resources of central banks. The market value of global long-term securities is approaching $100 trillion. Carry trade and foreign exchange markets have become huge.

In theory, central banks can expand their balance sheets without limit. In practice, they are constrained by the potential inflationary impact of their actions.

The current credit crisis will come to an end when the overhang of inventories of newly built homes is largely liquidated, and home price deflation comes to an end. That will stabilize the now-uncertain value of the home equity that acts as a buffer for all home mortgages, but most importantly for those held as collateral for residential mortgage-backed securities. Very large losses will, no doubt, be taken as a consequence of the crisis. But after a period of protracted adjustment, the U.S. economy, and the world economy more generally, will be able to get back to business.