Causes of the Great Depression In 1929 the stock market crashed, triggering the worst depression ever in U.S. history, which lasted for about a decade. During the 1920s, the unequal distribution of wealth and the stock market speculation combined to create an unstable economy by the end of the decade. The unequal distribution of the wealth had several outlets. Money was distributed between industry and agriculture within the U.S.; in social classes, between the rich and middle class; and lastly in world markets, between America and Europe. Due to the imbalance of the wealth, the economy became very unstable. The stock market cr