The cross-sectional variation of U.S. stock returns has been unusually high
in the past few years, The wide dispersion in security returns has led to
correspondingly wide dispersion in fund returns. For example, the cross-sec
tional standard deviation of returns on actively managed domestic equity mu
tual funds was 24 percent in 1999, compared with only 5 percent in 1996, We
argue that the wide dispersion in fund performance is a natural result of
increased security return dispersion and has little to do with changes in t
he informational efficiency of the market or the range of managerial talent
. The dramatic increase in return dispersion warrants a reexamination of tr
aditional methodologies for measuring fund performance that implicitly assu
me constant dispersion. We show how performance benchmarking can be extende
d to incorporate the information embedded in return dispersion, as well as
the benchmark mean return, by correcting fund alphas with a period- and ass
et-class-specific measure of security return dispersion.