The depression started in the United States after a major fall in stock prices that began around September 4, 1929, and became worldwide news with the stock market crash of October 29, 1929 (known as Black Tuesday). Between 1929 and 1932, worldwide gross domestic product (GDP) fell by an estimated 15%. By comparison, worldwide GDP fell by less than 1% from 2008 to 2009 during the Great Recession. Some economies started to recover by the mid-1930s. However, in many countries, the negative effects of the Great Depression lasted until the beginning of World War II.
The Great Depression had devastating effects in countries both 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 communities and rural areas suffered as crop prices fell by about 60%. Facing plummeting demand with few alternative sources of jobs, areas dependent on primary sector industries such as mining and logging suffered the most.
Economic historians usually attribute the start of the Great Depression to the sudden devastating collapse of U.S. stock market prices on October 29, 1929, known as Black Tuesday. However, some dispute this conclusion and see the stock crash as a symptom, rather than a cause, of the Great Depression.
Even after the Wall Street Crash of 1929 optimism persisted for some time. John D. Rockefeller said "These are days when many are discouraged. In the 93 years of my life, depressions have come and gone. Prosperity has always returned and will again." The stock market turned upward in early 1930, returning to early 1929 levels by April. This was still almost 30% below the peak of September 1929.