Interwar deflation and depression

Interwar macroeconomic history is a natural place to look for evidence on the correlations between (a) deflation and depression and (b) unexpected deflation and depression. We apply time-series methods to measure unexpected deflation or inflation for 26 countries from 1922 to 1939. The results suggest much variation across countries in the degree to which the ongoing deflation of the 1930s was unexpected. There is a significant, positive correlation between deflation and depression for the entire period but relatively little evidence of a role for unexpected deflation.