Causes of the Great Depression
Second, there are the monetarists, who believe that the Great Depression started as an ordinary recession, but that significant policy mistakes by monetary authorities (especially the Federal Reserve) caused a shrinking of the money supply which greatly exacerbated the economic situation, causing a recession to descend into the Great Depression. Related to this explanation are those who point to debt deflation causing those who borrow to owe ever more in real terms.
Depression (economics)
The best-known depression was the Great Depression, which affected most national economies in the world throughout the 1930s. This depression is generally considered to have begun with the Wall Street Crash of 1929, and the crisis quickly spread to other national economies. Between 1929 and 1933, the gross national product of the United States decreased by 33% while the rate of unemployment increased to 25% (with industrial unemployment alone rising to approximately 35% – U.S. employment was still over 25% agricultural).