From the middle of 2006 there was a dramatic rise in mortgage delinquencies across the breadth of the United States. A foreclosure epidemic had been triggered. House prices had initially peaked and then begun a steep decline. At the same time interest rates had continued to rise. When the introductory period of adjustable rate mortgages (issued mostly to the subprime2 mortgage market) ended and the low interest rate ceased, mortgage payments ballooned. Mortgage refinancing for homeowners became either more expensive or impossible. In the period from July 2006 to July 2007 the rate of foreclosures (home repossessions) had risen by 93% (RealityTrac), as homeowners continued to default on their mortgages.3 In the same year this number grew to 1.5 million before it began to decline (Bernanke 2008b). As a result of the foreclosures, securities backed with subprime mortgages widely held by investors lost most of their value. In addition, as mortgage losses mounted, investors questioned the reliability of the credit ratings, especially those of structured credit products.4 Since many investors had not performed independent valuations of these often complex instruments, the loss in confidence in the credit ratings led to a sharp decline in the willingness of investors to purchase these products. Liquidity dried up. Prices fell. Many of these investors had assumed significant debt burdens to invest in these securities. Rather than using the boom period to build theirreserves, investors (banks) increased their risk exposure as evidenced by higher debt to equity ratios, also known as financial leverage. As a result, investors did not have a sufficiently large financial cushion to absorb extensive loan defaults when they arose. The consequence was a large decline in the capital of many US banks. However, the problems were not restricted to US banks, as outlined in Box 4.1.