Differential Information and Performance Measurement Using a Security Market Line
Philip H. Dybvig, Stephen A. Ross · The Journal of Finance · 1985
An uninformed observer using the tools of mean variance and security market line analysis to measure the performance of a portfolio manager who has superior information is unlikely to be able to make any reliable inferences. While some positive results of a very limited nature are possible, e.g., when there is a riskless asset or when information is restricted to be “security specific,” in general anything is possible. In particular, a manager with superior information can appear to the observer to be below or above the security market line and inside or outside of the mean-variance efficient frontier, and any combination of these is possible.