Following the Wall Street Crash of 1929 and the Great Depression, Irving Fisher developed the theory that recessions and depressions are due to the overall level of debt shrinking (deflating).
It looks something like this:
1. Debt liquidation leads to distress selling and to
2. Contraction of deposit currency, as bank loans are paid off, and to a slowing down of velocity of circulation. This contraction of deposits and of their velocity, precipitated by distress selling, causes
3. A fall in the level of prices, in other words, a swelling of the dollar. Assuming, as above stated, that this fall of prices is not interfered with by reflation or otherwise, there must be
4. A still greater fall in the net worths of business, precipitating bankruptcies and
5. A like fall in profits, which in a “capitalistic,” that is, a private-profit society, leads the concerns which are running at a loss to make
6. A reduction in output, in trade and in employment of labor. These losses, bankruptcies and unemployment, lead to
7. Pessimism and loss of confidence, which in turn lead to
8. Hoarding and slowing down still more the velocity of circulation.
The above eight changes causes
9. Complicated disturbances in the rates of interest, in particular, a fall in the nominal, or money, rates and a rise in the real, or commodity, rates of interest.
Here is the full paper by Fisher: