Wall Street did not start the Great Depression. The Great Depression was a severe worldwide economic depression that began in the United States in the 1930s. The global gross domestic product (GDP) decreased by an estimated 15% from 1929 and 1932. During the Great Recession, global GDP decreased by less than 1% from 2008 to 2009. The Great Depression was the longest, deepest, and most widespread decline in the 20th century.