Overborrowing and systemic externalities in the business cycle

Credit constraints that link a private agent’s debt to market-determined prices embody a credit externality that drives a wedge between competitive and constrained socially optimal equilibria, inducing private agents to overborrow. The externality arises because agents fail to internalize the debt-deflation effects of additional borrowing when negative income shocks trigger the credit constraint. We quantify the effects of this inefficiency in a two-sector dynamic stochastic general equilibrium model of a small open economy calibrated to emerging markets. The credit externality increases the probability of financial crises by a factor of seven and causes the maximum drop in consumption to increase by 10 percentage points.