Robustness and Ambiguity Aversion in General Equilibrium

We analyze the empirical predictions of ambiguity aversion in intertemporal heterogenous agents economies. We examine equilibria for two tractable wealth--homothetic settings of ambiguity aversion in continuous time. Each setting is motivated by a different robust control optimization problem. We show that ambiguity aversion affects optimal portfolios in a way that is similar to an increase in risk aversion. A distinct property of our second setting of ambiguity aversion is that this increase is state dependent, highly pronounced at moderate portfolio exposures and reduces equity-market participation. In general equilibrium, ambiguity aversion raises the equity premium and lowers interest rates. A distinct feature of our second setting of ambiguity aversion is that the equity premium part due to ambiguity aversion dominates when volatility is low.