Table of Contents: Masthead StickySummary List PlacementMany factors contributed to the Great Recession of 2007 to 2009, the second-worst economic crisis in US history. What caused this economic chaos? Economists cite as the main culprit the collapse of the subprime mortgage market — defaults on high-risk housing loans — which led to a credit crunch in the global banking system and a precipitous drop in bank lending. But, in fact, the reasons are more complex.