Roberto Tallarita is a Lecturer on Law and Associate Director of the Program on Corporate Governance at Harvard Law School. This post is based on his recent paper. Related research from the Program on Corporate Governance includes The Agency Problems of Institutional Investors by Lucian Bebchuk, Alma Cohen, and Scott Hirst (discussed on the Forum here); 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 Specter of the Giant Three by Lucian Bebchuk and Scott Hirst (discussed on the Forum here).
According to a theory that is gaining increasing support among academics and market participants (“portfolio primacy theory”), we should expect the “Big Three” (BlackRock, Vanguard, and State Street) and other index fund managers to push companies to reduce their climate externalities and thus mitigate the threat of climate change. In a new paper, The Limits of Portfolio Primacy, I question the implicit and explicit assumptions of this theory and show its significant limits. My analysis reveals that the theory’s optimistic take on the social role of index funds is grossly overstated, and suggests that climate policy should not rely on index fund stewardship as a substitute for traditional regulation.
The basic premise of the portfolio primacy theory is that the goal of index fund managers and other diversified investors is not to maximize the value of individual companies (shareholder primacy), but rather to maximize the value of their entire portfolio (portfolio primacy). Index funds, the argument goes, mirror the whole economy and therefore internalize climate externalities. Even if an individual company has no incentives to reduce its own carbon emissions, index funds have strong incentives to push for such reduction.
But to what extent can index funds be expected to undertake the role of climate stewards? And how effective can they be in mitigating global climate risk? I identify four crucial limits of portfolio primacy: portfolio biases, mispricing of climate mitigation, fiduciary failures, and insulation from index fund influence. Taken together, these four limits should dramatically lower the expectations that portfolio primacy can be a powerful weapon in our fight against global climate change.