Today's economic condition could likely be seen as "the most wrenching since the end of the second world war," wrote former Federal Reserve chairman Alan Greenspan in the Financial Times on Monday.

The U.S. financial crisis won't end until housing prices stabilize, but that won't happen for months, wrote Greenspan.

The models used by the finance industry to determine risk and measure economic strength are too simple to fully account for human responses, he said. "We cannot hope to anticipate the specifics of future crises with any degree of confidence," he wrote.

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However, Greenspan said that he hoped the fallout would not take away the finance industry's ability to regulate itself. Market flexibility and free competition are the most reliable safeguards against economic trouble, he said; the system which is supposed to guard against unanticipated losses will need to be overhauled.