Debt deflation is a theory that recessions and depressions are due to the overall level of debt rising in real value because of deflation, causing people to default on their consumer loans and mortgages. Bank assets fall because of the defaults and because the value of their collateral falls, leading to a surge in bank insolvencies, a reduction in lending and by extension, a reduction in spending.
The theory was developed by Irving Fisher following the Wall Street Crash of 1929 and the ensuing Great Depression. The debt deflation theory was familiar to John Maynard Keynes prior to Fisher's discussion of it, but he found it lacking in comparison to what would become his theory of liquidity preference. The theory, however, has enjoyed a resurgence of interest since the 1980s, both in mainstream economics and in the heterodox school of post-Keynesian economics, and has subsequently been developed by such post-Keynesian economists as Hyman Minsky and by the neo-classical mainstream economist Ben Bernanke.
Fisher's formulation (1933) In Fisher's formulation of debt deflation, when the debt bubble bursts the following sequence of events occurs:
Rejection of previous assumptions
Prior to his theory of debt deflation, Fisher had subscribed to the then-prevailing, and still mainstream, theory of general equilibrium. In order to apply this to financial markets, which involve transactions across time in the form of debt – receiving money now in exchange for something in future – he made two further assumptions: (A) The market must be cleared—and cleared with respect to every interval of time. (B) The debts must be paid. In view of the Depression, he rejected equilibrium, and noted that in fact debts might not be paid, but instead defaulted on:
He further rejected the notion that over-confidence alone, rather than the resulting debt, was a significant factor in the Depression:
In the context of this quote and the development of his theory and the central role it places on debt, it is of note that Fisher was personally ruined due to his having assumed debt due to his over-confidence prior to the crash, by buying stocks on margin.
Other debt deflation theories do not assume that debts must be paid, noting the role that default, bankruptcy, and foreclosure play in modern economies.
Initial mainstream interest
Initially Fisher's work was largely ignored, in favor of the work of Keynes.
The following decades saw occasional mention of deflationary spirals due to debt in the mainstream, notably in The Great Crash, 1929 of John Kenneth Galbraith in 1954, and the credit cycle has occasionally been cited as a leading cause of economic cycles in the post-WWII era, as in , but private debt remained absent from mainstream macroeconomic models.
James Tobin cited Fisher as instrumental in his theory of economic instability.
Debt-deflation theory has been studied since the 1930s but was largely ignored by neoclassical economists, and has only recently begun to gain popular interest, although it remains somewhat at the fringe in U.S. media.
Ben Bernanke (1995) The lack of influence of Fisher's debt-deflation in academic economics is thus described by Ben Bernanke in : Fisher's idea was less influential in academic circles, though, because of the counterargument that debt-deflation represented no more than a redistribution from one group (debtors) to another (creditors). Absent implausibly large differences in marginal spending propensities among the groups, it was suggested, pure redistributions should have no significant macroeconomic effects.
Building on both the monetary hypothesis of Milton Friedman and Anna Schwartz as well as the debt deflation hypothesis of Irving Fisher, Bernanke developed an alternative way in which the financial crisis affected output. He builds on Fisher's argument that dramatic declines in the price level and nominal incomes lead to increasing real debt burdens, which in turn leads to debtor insolvency, thus leading to lowered aggregate demand and further decline in the price level, which develops into a debt deflation spiral. According to Bernanke a small decline in the price level simply reallocates wealth from debtors to creditors without doing damage to the economy. But when the deflation is severe, falling asset prices along with debtor bankruptcies lead to a decline in the nominal value of assets on bank balance sheets. Banks will react by tightening their credit conditions. That in turn leads to a credit crunch that does serious harm to the economy. A credit crunch lowers investment and consumption, which leads to declining aggregate demand, which additionally contributes to the deflationary spiral.