Alan Greenspan writes in the Financial Times: worst financial crises since WWII

"The current financial crisis in the US is likely to be judged in retrospect as the most wrenching since the end of the second world war. It will end eventually when home prices stabilise and with them the value of equity in homes supporting troubled mortgage securities.

Home price stabilisation will restore much-needed clarity to the marketplace because losses will be realised rather than prospective. The major source of contagion will be removed. Financial institutions will then recapitalise or go out of business. Trust in the solvency of remaining counterparties will be gradually restored and issuance of loans and securities will slowly return to normal. Although inventories of vacant single-family homes - those belonging to builders and investors - have recently peaked, until liquidation of these inventories proceeds in earnest, the level at which home prices will stabilise remains problematic.

The American housing bubble peaked in early 2006, followed by an abrupt and rapid retreat over the past two years. Since summer 2006, hundreds of thousands of homeowners, many forced by foreclosure, have moved out of single-family homes into rental housing, creating an excess of approximately 600,000 vacant, largely investor-owned single-family units for sale. Homebuilders caught by the market's rapid contraction have involuntarily added an additional 200,000 newly built homes to the "empty-house-for-sale" market."