The implications of market efficiency for money managers, which is supported by real-world data for at least 10-year periods, is that in a given year, the majority of professional money managers will never outperform a broad measure of the U.S. stock market. it is impossible for a professional money manager to beat the performance of a broad measure of the U.S. stock market over any time period. in the long-run, the majority of professional money managers will not outperform a broad measure of the U.S. stock market