The power of passive investors is a double-edged sword, experts argue

Since the financial crisis of 2008, the stock market has seen a remarkable migration of investor money away from active management and toward passive, or index, funds. As a result, the "Big Three" asset managers—BlackRock, Vanguard and State Street—have swiftly ballooned into behemoths. Taken together, they constitute the largest shareholder in more than 40% of publicly traded U.S. firms, and 88% of the S&P 500.