We find that the stocks that active managers display the most conviction towards ex-ante, their “Best Ideas,” outperform the market, as well as the other stocks in those managers' portfolios, by approximately 2.5 to 4.5 percent per year, depending on the benchmark employed. The other stocks managers hold do not exhibit significant outperformance. Thus, the organization of the money management industry appears to make it optimal for managers to introduce stocks into their portfolio that are not outperformers. We argue that investors would benefit if managers held more concentrated portfolios.