The global financial crisis of 2007-2009 was caused by the collapse of markets for bonds backed by mortgages in the US. When these bonds became worthless, banks holding them went bankrupt, leading to a worldwide credit crisis. To prevent a total financial collapse, governments bailed out banks with billions of dollars. Stock markets plummeted, wiping out trillions of dollars in wealth. This crisis triggered the worst US recession since the Great Depression, with millions of jobs lost and high unemployment rates. Experts attribute the crisis to the alleged irrational behavior of sophisticated investors.