Former Federal Reserve Chairman Alan Greenspan said the current financial crisis is a «once-in-a-century credit tsunami» which will have a severe impact on the U.S. economy, driving unemployment higher, AP reported. Greenspan, who headed the U.S. central bank for 18 1/2 years, said he and others who believed lending institutions would do a better job at protecting their shareholders are in a «state of shocked disbelief.» In testimony prepared for the House Oversight Committee on Thursday, Greenspan blames the problems on heavy demand for securities backed by subprime mortgages by investors who did not worry that the boom in home prices might come to a crashing halt.