The Great Depression was caused by the financial devastation of World War I, with the US loaning money to allies who did not repay, the failure of the Federal Reserve to control interest rates, and the Smoot-Hawley Tariff Act raising prices of foreign goods and reducing US exports. This led to about 1/3 of the workforce becoming unemployed even as Hoover and later FDR created numerous government programs to stimulate the economy and help the unemployed in the face of the crisis.