Deleverage and financial fragility

Severe economic downturns, characterized by deleverage, are typically preceeded by phenomena of debt overhang. This evidence suggests that large recessions may not be the result of large shocks, but, rather, of the interaction between typical shocks and the current state of the economy. We study the transmission of deleverage shocks in a stochastic economy with heterogeneous agents and occasionally binding collateral constraints, where debt evolves endogenously. Our key finding is that the impact effect of a deleverage shock on aggregate output is a non-linear, S-shaped, function of the accumulated level of debt. At low levels of debt, deleverage is almost neutral, whereas its negative impact is largely magnified when debt reaches a critical threshold, i.e., when financial fragility is sufficiently high. At this threshold, the constraint on borrowing becomes endogenously binding. However, when the level of debt is already high before the shock hits, the borrowers are constrained both ex-ante and ex-post. In this case, the effect on output of a deleverage shock is the highest, but, at the margin, roughly insensitive to the level of debt. This non-linearity is much more pronounced for deleverage shocks than for productivity shocks. Our results cast doubts on the accuracy of gauging the effects of financial disturbances in linearized, certainty-equivalence environments.