Edward B. Rock is the Martin Lipton Professor of Law at New York University School of Law and Daniel L. Rubinfeld is Professor of Law at New York University School of Law. This post is based their recent paper. Related research from the Program on Corporate Governance includes Horizontal Shareholding (discussed on the Forum here) and New Evidence, Proofs, and Legal Theories on Horizontal Shareholding (discussed on the Forum here) both by Einer Elhauge; Index Funds and the Future of Corporate Governance: Theory, Evidence, and Policy by Lucian Bebchuk and Scott Hirst (discussed on the forum here); and The Agency Problems of Institutional Investors by Lucian Bebchuk, Alma Cohen, and Scott Hirst (discussed on the Forum here).
There is compelling evidence that both concentration and profitability in oligopolistic industries have increased over the past two decades. Over roughly the same time period, the concentration of shareholding in the hands of the largest institutional investors has dramatically increased, with an increase in the degree to which investors (such as Vanguard, State Street and BlackRock) own large equity stakes in competing portfolio companies. A number of authors—focusing initially on airlines and commercial banking—have argued that the growth in this “common ownership” has caused the increase in oligopoly profits. They have followed this with a variety of policy responses.
We start with the core puzzle. The “Structure-Conduct-Performance paradigm”—which asserts a connection between concentration and profits—has long been a staple of antitrust policy. Yet, compelling empirical support for this connection has historically been sparse, for reasons well discussed in the Industrial Organization literature. Interestingly, according to the empirical evidence, something changed around 2000. Since then, the evidence for a link between concentration and profitability has become quite strong. As a result, an adequate theory must explain two things. First, why is there a correlation between concentration and profitability? Second, why has there been a strong(er) correlation post 2000 than pre-2000?