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 the Great Depression
Barber says, while there is "no clear evidence" of a decline in "the rate of growth of productivity" during the 1920s, there is "clear evidence" the population growth rate began to decline during that same period. He argues the decline in population growth rate may have caused a decline in "the natural rate of growth" which was significant enough to cause a serious depression.