Our result,that investors appear to be using the CAPM to
make their investment decisions, is very surprising in light
of the well documented failure of the CAPM to adequately
explain the cross-sectional variation in expected stock
returns. Although, ultimately, we leave this as apuzzle to be
explained by future research, we do note that the poor
performance of the reduced form factor model srelative to
the CAPM implies that investors do not use the additional
factors in those models to measure risk. Much of the flows
in and out of mutual funds remain unexplained. To that end
the paper leaves as an unanswered question whether the
unexplained part of flows results because investors use a
superior, yet undiscovered, risk model, or whether investors
use other, non-risk-based, criteria to make investment
decisions.