Irving Fisher's theory of how paying down debt can deepen a depression

Irving Fisher argued that when over-indebted borrowers rush to sell assets and repay loans, the resulting fire sales push prices down, which raises the real burden of the debt still owed and forces even more selling. He laid out this self-reinforcing spiral in a 1933 paper, written not long after he lost much of his own fortune in the 1929 crash, and it became a template for explaining the Great Depression.

— Irving Fisher, The Debt-Deflation Theory of Great Depressions — Econometrica, 1933