The most important trend in fiduciary investing over the past 30 years has been the application of the theory of efficient markets or modern portfolio theory. Because the market price of a security already impounds the information that is known or knowable about the future prospects of that security, it is quite difficult even for investment professionals to identify overpriced securities to sell and underpriced securities to buy. Evidence has accumulated that professional investors managing large portfolios have regularly underperformed the broad market averages like the Standard & Poor's 500. Mutual fund portfolios have been extensively studied. Adjusting for costs, the average mutual fund underperforms the market averages. There does not appear to be consistent exceptions: some funds do better than others, but across long periods of time few, if any, have outperformed the market with a consistency greater than the law of averages would predict. In a sense, these findings flow naturally from the magnitude of pension and mutual fund holdings.