Passive institutional investors are an increasingly important component of U.S. stock ownership. To examine whether and by which mechanisms passive investors influence firms' governance, we exploit variation in ownership by passive mutual funds associated with stock assignments to the Russell...

We document that institutional investors, and particularly hedge funds, increased their holdings of smaller stocks from 1980 to 2010 and decreased their holdings of larger stocks. As of 1990 institutions began to underweight, relative to market weights, those stocks that make up the largest 40...