A period that began with the stock market crash in October 1929 that turned into a worldwide economic collapse. Real gross national product in the U.S. declined from October 1929 until March 1933 by 24 percent. A large number of banks and businesses failed, which added to the malaise. International trade also declined sharply as countries passed trade protectionist legislation. When recovery began, it failed to make up the earlier losses and the effects of the depression continued until World War II began in 1939. During the 1929 to 1933 period, unemployment was above 20 percent.