This paper provides the first empirical test of the diversification of opinions theory and the group shift theory using real business data. Our data set covers management teams and single managers of US equity mutual funds. Our results reject the group shift theory and support the...

Whether teams attenuate or exacerbate the behavioral biases which are pervasive at the individual level is an open question. To address this question, we use the mutual fund industry as a laboratory. Our focus is on how return extrapolation, a bias in investor behavior that has received...