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.
Causes of unemployment in the United States
During the Great Depression, "hard core" structural unemployment was very common. Hard-core unemployment refers to individuals that have been unemployed for a prolonged period of time (i.e. six months, over a year). The hard core unemployment phenomenon present in the 1930s is believed to be caused by not only the depression, but also a shift in business personnel policies. In the 1920s, businessmen found the most profitable wage to be the "efficiency wage", one that attracted more productive workers. This resulted in new policies designed to find trained, efficient workers, and to encourage other workers to become more like them.