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.
Ben Bernanke
Bernanke is particularly interested in the economic and political causes of the Great Depression, on which he has published numerous academic journal articles. Before Bernanke's work, the dominant monetarist theory of the Great Depression was Milton Friedman's view that it had been largely caused by the Federal Reserve's having reduced the money supply and has on several occasions argued that one of the biggest mistakes made during the period was to raise interest rates too early. In a speech on Milton Friedman's ninetieth birthday (November 8, 2002), Bernanke said:
"Let me end my talk by abusing slightly my status as an official representative of the Federal Reserve. I would like to say to Milton and Anna [Schwartz, Friedman's coauthor]: Regarding the Great Depression, you're right. We did it. We're very sorry. But thanks to you, we won't do it again."