Not fooled by randomness: Using random portfolios to analyse investment funds

Abstract

The biggest challenge in testing mutual funds for manager skill is the lack of a probability distribution of returns under the null hypothesis of no skill. A methodology based on randomly trading portfolios and non parametric statistical tests is explored, and a test of skill is proposed. Empirical tests performed on a sample of US equity mutual funds find evidence of skill in a reduced number of managers, but the value added by this skill is charged away from the investors in the form of fund fees and expenses. Overall, random portfolio based measures are found to be more powerful and easier to interpret than tests based on traditional and bootstrapped factor model alphas.