"The Depression was preceded by a period of industrial growth and social development known as the "Roaring Twenties". Much of the profit generated by the boom was invested in speculation, such as on the stock market, contributing to growing wealth inequality. Banks were subject to minimal regulation, resulting in loose lending and widespread debt. By 1929, declining spending had led to reductions in manufacturing output and rising unemployment. Share values continued to rise until the October 1929 crash, after which the slide continued until July 1932, accompanied by a loss of confidence in the financial system. By 1933, the U.S. unemployment rate had risen to 25%, about one-third of farmers had lost their land, and 9,000 of its 25,000 banks had gone out of business. President Herbert Hoover was unwilling to intervene heavily in the economy, and in 1930 he signed the Smoot–Hawley Tariff Act, which worsened the Depression. In the 1932 presidential election, Hoover was defeated by Franklin D. Roosevelt, who from 1933 pursued a set of expansive New Deal programs in order to provide relief and create jobs. In Germany, which depended heavily on U.S. loans, the crisis caused unemployment to rise to nearly 30% and fueled political extremism, paving the way for Adolf Hitler's Nazi Party to rise to power in 1933. Between 1929 and 1932, worldwide gross domestic product (GDP) fell by an estimated 15%; in the U.S., the Depression resulted in a 30% contraction in GDP."
https://en.wikipedia.org/wiki/Great_Depression