Passive investors — ETFs and index funds — are the most important development in modern day capital markets, dictating trillions of dollars in capital flows and increasingly owning much of corporate America. Neither the business model of passive funds, nor the way that they engage with their portfolio companies, however, is well understood, and misperceptions of both have led some commentators to call for passive investors to be subject to increased regulation and even disenfranchisement. Specifically, this literature takes a narrow view both of the market in which passive investors compete to manage customer funds and of passive investors’ participation in the capital markets.We respond to this failure by providing the first comprehensive theoretical framework for passive investment and its implications for corporate governance. To start, we explain that, to understand passive funds, it is necessary to understand the institutional context in which they operate. Two key insights follow. First, because passive funds are simply a pool of assets – their incentives are a product of the overall business operations of fund sponsors. Second, although passive funds are locked into their investments, their shareholders are not. Like all mutual fund investors, shareholders in index funds can exit at any time by selling their shares and receiving the net asset value of their ownership interest. Consequently, the sponsors of passive funds must compete on both price and performance with other investment options – including both other passive funds and actively-managed funds -- for investor dollars. As we explain, this competition provides passive fund sponsors with a variety of incentives to engage. Furthermore, the size of the major fund sponsors and the breadth of their holdings affords them economies of scale enabling them to engage effectively.An examination of passive investor engagement in corporate governance demonstrates that passive investors behave in accordance with this theory. Passive investors are devoting greater sophistication and resources to engagement with their portfolio companies and are exploiting their comparative advantages – their size, breadth of portfolio and resulting economies of scale -- to focus on issues with a broad market impact, such as potential corporate governance reforms, that have the potential to reduce the underperformance and mispricing of portfolio companies. Passive investors use these tools, as opposed to analyzing firm-specific operational issues, to reduce the relative advantage that active funds gain through their ability to trade.We conclude by exploring the overall implications of the rise of passive investment for corporate law and financial regulation. We argue that, although existing critiques of passive investors are unfounded, the rise of passive investing raises new concerns about ownership concentration, conflicts of interest and common ownership. We evaluate these concerns and the extent to which they warrant changes to existing regulation and practice
