Single-Name Credit Risk, Portfolio Risk, and Credit Rationing

Abstract

This paper introduces non-diversifiable risk in the Stiglitz-Weiss adverse selection model, so that an increase in the average riskiness of the borrower pool causes higher portfolio risk. This opens up the possibility of equilibrium credit rationing. Comparative statics analysis shows that an increase in risk aversion turns a two-price equilibrium into a rationing equilibrium. A two-price equilibrium is more inefficient than a rationing equilibrium, and a usury law that rules out the higher of the two interest rates can be welfare-improving. Contrary to the common result, the equilibrium may be characterized by over-investment.