This thesis presents three essays. The first chapter examines the information content of aggregate mutual fund alpha. Recent evidence shows that mutual funds collectively buy overvalued stocks. I hypothesize that aggregate alpha arises in part from such stocks becoming even more overvalued, and thus is a measure of market overvaluation. A one-standard-deviation increase in aggregate alpha corresponds to a 0.83 percentage point decrease in the following month's excess market return, and aggregate alpha yields a monthly out-of-sample R2 of 3.64%. Moreover, higher aggregate alpha predicts higher anomaly returns and lower aggregate earnings surprises. The market-return predictability stems from funds with high investment in overvalued stocks, a...