Dynamic Equilibrium with Liquidity Constraints

We consider an intertemporal economy with liquidity constrained and unconstrained individuals. A liquidity constraint prevents marketability of future income and thus endogenously generates market incompleteness. In contrast with the existing literature on portfolio constraints, our liquidity constraints arise naturally whenever agents may default and have a finite horizon. Liquidity constrained individuals optimally (i) postpone consumption in early age and (ii) experience permanent consumption increases whenever the constraint binds. The equilibrium interest rate and asset prices are characterized under very general assumptions on preferences and endowment processes. In the presence of liquidity constraints, the cumulative interest return is reduced. In addition, the CCAPM holds, even when the basic market structure is incomplete. With homogeneous relative risk aversion market incompleteness reinforces the effect of liquidity constraints and further reduces the riskless return. However, we show that neither incompleteness nor liquidity constraints can explain the empirical magnitude of the Sharpe ratio for admissible levels of risk aversion, independently of preferences and endowment assumptions. Additional contributions of the paper include (i) a new characterization of the consumption-portfolio problem of constrained individuals leading to an explicit solution, (ii) a constructive approach to the determination of equilibrium, and (iii) a numerical procedure to handle the forward-backward path-dependent computational problem arising with a liquidity constraint.
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