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.
Great Depression
Between 1933 and 1939, federal expenditure tripled, and Roosevelt's critics charged that he was turning America into a socialist state. The Great Depression was a main factor in the implementation of social democracy and planned economies in European countries after World War II (see Marshall Plan). Keynesianism generally remained the most influential economic school in the United States and in parts of Europe until the periods between the 1970s and the 1980s, when Milton Friedman and other neoliberal economists formulated and propagated the newly created theories of neoliberalism and incorporated them into the Chicago School of Economics as an alternative approach to the study of economics. Neoliberalism went on to challenge the dominance of the Keynesian school of Economics in the mainstream academia and policy-making in the United States, having reached its peak in popularity in the election of the presidency of Ronald Reagan in the United States, and Margaret Thatcher in the United Kingdom.