Asset Demand and Ambiguity Aversion

We study the optimal portfolio choice problem of an investor who is averse to both risk and ambiguity. Using the class of utility functions proposed by Klibano, Marinacci, and Mukerji (2005), we establish a generalized mutual fund theorem, which shows that there are a xed number of mutual funds that cater for all investors, regardless of their ambiguity aversion. We prove that the optimal portfolio is decomposed into two, one remaining and the other vanishing as the degree of ambiguity aversion goes to innity. We also introduce factor models with ambiguity and compare our results with the Bayesian portfolio approach.