Along but beyond mean-variance : Utility maximization in a semimartingale model

Abstract

It is well known that under certain assumptions the strategy of an investor maximizing his expected utility coincides with the mean-variance optimal strategy. In this paper we show that the two strategies are not equal in general and find the connection between a utility maximizing and a mean-variance optimal strategy in a continuous semimartingale model. That is done by showing that the utility maximizing strategy of a CARA investor can be expressed in terms of expectation and the expected quadratic variation of the underlying price process. It coincides with the mean-variance optimal strategy if the underlying price process is a local martingale. Keywords: mean-variance portfolios, utility maximization, dynamic portfolio selection, quadratic variation JEL classification numbers: G11, C61