The Great Depression was a severe worldwide economic depression that took place mostly during the 1930s, beginning in the United States. The timing of the Great Depression varied around the world; in most countries, it started in 1929 and lasted until the late 1930s. It was the longest, deepest, and most widespread depression of the 20th century. The Great Depression is commonly used as an example of how intensely the global economy can decline.

The Great 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, which was 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 both rich and poor countries. Personal income, tax revenue, profits and prices dropped, while international trade fell by more than 50%. Unemployment in the U.S. rose to 23% and in some countries rose as high as 33%. Cities 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 consider the catalyst of the Great Depression to be the sudden devastating collapse of U.S. stock market prices, starting on October 24, 1929. 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, where the Dow Jones Industrial Average dropped from 381 to 198 over the course of two months, optimism persisted for some time. The stock market turned upward in early 1930, with the Dow returning to 294 (pre-depression levels) in April 1930, before steadily declining for years, to a low of 41 in 1932.

At the beginning, governments and businesses spent more in the first half of 1930 than in the corresponding period of the previous year. On the other hand, consumers, many of whom suffered severe losses in the stock market the previous year, cut their expenditures by 10%. In addition, beginning in the mid-1930s, a severe drought ravaged the agricultural heartland of the U.S.

Interest rates dropped to low levels by mid-1930, but expected deflation and the continuing reluctance of people to borrow meant that consumer spending and investment remained low. By May 1930, automobile sales declined to below the levels of 1928. Prices, in general, began to decline, although wages held steady in 1930. Then a deflationary spiral started in 1931. Farmers faced a worse outlook; declining crop prices and a Great Plains drought crippled their economic outlook. At its peak, the Great Depression saw nearly 10% of all Great Plains farms change hands despite federal assistance.

The decline in the U.S. economy was the factor that pulled down most other countries at first; then, internal weaknesses or strengths in each country made conditions worse or better.[citation needed] Frantic attempts by individual countries to shore up their economies through protectionist policies – such as the 1930 U.S. Smoot–Hawley Tariff Act and retaliatory tariffs in other countries – exacerbated the collapse in global trade, contributing to the depression. By 1933, the economic decline pushed world trade to one third of its level compared to four years earlier. (Wikipedia)