Jeffrey Coles is the Samuel S. Stewart, Jr. Presidential Chair in Business, David Eccles Chair, and Professor of Finance; Davidson Heath is an Assistant Professor of Finance; and Matthew Ringgenberg is an Associate Professor of Finance, all at the University of Utah David Eccles School of Business. This post is based on their recent paper, forthcoming in the Journal of Financial Economics.
Related research from the Program on Corporate Governance includes The Agency Problems of Institutional Investors (discussed on the Forum here) by Lucian Bebchuk, Alma Cohen, and Scott Hirst; Index Funds and the Future of Corporate Governance: Theory, Evidence, and Policy (discussed on the forum here) and The Specter of the Giant Three (discussed on the Forum here), both by Lucian Bebchuk and Scott Hirst; and The Limits of Portfolio Primacy (discussed on the Forum here) by Roberto Tallarita.
The last two decades have seen a dramatic increase in the amount of capital invested in passive index funds. While these funds help investors earn benchmark index returns for relatively low fees, the increase in passive investing is not without controversy. Passive investors, by definition, hold portfolios that simply track an index. As a result, they do not do research—they free-ride on the research and analysis of active investors. This leads to a tension: Not everyone can index, some investors must be active for prices to incorporate information. The question is, does the rise of passive investing change information production in the economy? If so, how does passive investing affect informational efficiency, that is, the link between stock prices and fundamental value?
In our paper On Index Investing (Journal of Financial Economics, 2022), we examine these questions, both theoretically and empirically. We first develop a model that is a simple extension of the classic Grossman-Stiglitz (1980) model of information acquisition by investors. We then test the model’s predictions using Russell index reconstitutions as a shock to the mix of passive and active investors. Our findings suggest that passive investing does reduce information production, but perhaps surprisingly, it does not harm informational efficiency.
Existing theories disagree on the relation between investor composition and market efficiency. Some models predict that the rise of passive investing does alter price efficiency. For example, as passive funds replace active funds, there are fewer active funds doing research which could make prices less efficient.

