By TheStreet.com Staff What Was the Great Recession? How Long Did It Last? The most severe economic downturn since World War II occurred between December 2007 and June 2009. During this period, hundreds of banks failed, millions of homes went into foreclosure, and Americans lost over $14 trillion in net worth. Unemployment levels swelled from 5% in 2007 to 10% in 2009. Arecession is defined as two consecutive quarters of contraction in gross domestic product (GDP). During a recession, companies fold, people lose their jobs, and manufacturing output declines on lower demand. The recession of 20…