They point out that between 19, the Federal Reserve allowed the money supply (Measured by M2) to fall by a third.
In particular, Monetarists such as Friedman criticise the decisions of the Fed not to save banks going bankrupt.
The Austrian school doesn't accept the Friedman analysis that falling money supply was the main problem.
They argue it was the loss of confidence in the banking system which caused the most damage.
Therefore, the unemployed dramatically reduced their spending.
America had lent substantial amounts to Europe and UK, to help rebuild after first world war.
Furthermore, they pointed to the Soviet Union as a country which was able to overcome the great depression through state-sponsored economic planning.
The stock market crash of October 1929, was certainly a factor which precipitated events.
On Tuesday there was another collapse in prices known as 'Black Tuesday'.
Although shares recovered a little in 1930, confidence had evaporated and problems spread to the rest of the financial system.