Asset Pricing With Heterogeneous Risk Aversion and Portfolio Constraints

Abstract

This paper analyzes the effects of portfolio constraints on asset returns and volatility. Portfolio constraints may arise due to minimum capital requirement regulations, margin requirements or leverage constraints on portfolio managers. We analyze how cross-sectional heterogeneity in preferences affect the equilibrium stock price, returns and volatility in the presence of portfolio constraints. We show that portfolio constraints can simultaneously produce high equity Sharpe ratio and low interest rates in equilibrium. Moreover, the stock returns volatility decreases when the constraint binds. The negative effect of the constraint on stock returns volatility is most pronounced when the constraint binds in the bad state of the economy and the unconstrained investor is poorer than the constrained investor. In our model the constraint binds more frequently in the bad states of the economy. Given the empirical evidence in support of the stylized fact that stock returns volatility is counter-cyclical, our findings therefore suggest that margin requirements are indeed effective in mitigating the wild fluctuations in the stock market volatility when prices go low. We also perform a welfare analysis and show that the unconstrained investor is made better off while the constrained is worse off when the constraint binds.