Greenspan admitted that he had put too much faith in the self-correcting power of free markets and had failed to anticipate the self-destructive power of wanton mortgage lending.
Mr. Greenspan refused to accept blame for the crisis but acknowledged that his belief in deregulation had been shaken.
He noted that the immense and largely unregulated business of spreading financial risk widely, through the use of exotic financial instruments called derivatives, had gotten out of control and had added to the havoc of today's crisis. As far back as 1994, Mr. Greenspan staunchly and successfully opposed tougher regulation on derivatives.
Many Republican lawmakers on the oversight committee tried to blame the mortgage meltdown on the unchecked growth of Fannie Mae and Freddie Mac, the giant government-sponsored mortgage-finance companies that were placed in a government conservatorship last month.
Republicans have argued that Democratic lawmakers blocked measures to reform the companies.
But Mr. Greenspan, who was first appointed by President Ronald Reagan, placed far more blame on the Wall Street companies that bundled subprime mortgages into pools and sold them as mortgage-backed securities.
Global demand for the securities was so high, he said, that Wall Street companies pressured lenders to lower their standards and produce more ï¿½??paper.ï¿½??