The Great Depression was a severe worldwide economic depression in the decade preceding World War II. In most countries the depression started in about 1929 and lasted until the late 1930s or early 1940s. It was the longest, most widespread, and deepest depression of the 20th century. In the 21st century, the Great Depression is commonly used as an example of how far the world's economy can decline.
The depression originated in the U.S. Economic historians usually attribute the start of the Great Depression to the sudden devastating collapse of US stock market prices on October 29, 1929, known as Black Tuesday; some dispute this conclusion, and see the stock crash as a symptom, rather than a cause, of the Great Depression
There were multiple causes for the first downturn in 1929 but the real causes are still unclear. Historians emphasize structural factors like major bank failures and the stock market crash. In contrast, some economists point to monetary factors such as actions by the US Federal Reserve that contracted the money supply, as well as Britain's decision to return to the Gold Standard at pre–World War I parities.
The Great Depression had devastating effects in virtually every country, rich and poor. Personal income, tax revenue, profits and prices dropped, while international trade plunged by more than 50%. Unemployment in the U.S. rose to 25%, and in some countries rose as high as 33%. Cities all around the world were hit hard, especially those dependent on heavy industry. Construction was virtually halted in many countries. Farming and rural areas suffered as crop prices fell by approximately 60%. Facing plummeting demand with few alternate sources of jobs, areas dependent on primary sector industries such as cash cropping, mining and logging suffered the most.
Some economies started to recover by the mid-1930s; in many countries the negative effects of the Great Depression lasted until the start of World War II