2025 Zayira Ray
Julius Silver Professor, Faculty of Arts and Science,
Professor of Economics, New York University
Research Associate, NBER
Part-Time Professor, University of Warwick
Research Fellow, CESifo
Spool Member, ThReD

Department of Economics, 
New York University,
19 West 4th Street
New York, NY 10012, U.S.A.
debraj.ray@nyu.edu, +1 (212)-998-8906.

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Oxford University Press, 2008. This book is now open-access; feel free to download a copy, and to buy the print version if you like the book.
≋ Three Randomly Selected Papers
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On the Dynamics of Inequality

Economic Theory 29, 291–306, 2006.

Summary. The dynamics of inequality are studied in a model of human capital accumulation with credit constraints. This model admits a multiplicity of steady state skill ratios that exhibit varying degrees of inequality across households. The main result studies nonstationary equilibrium paths, and shows that an equilibrium sequence of skill ratios must converge monotonically to the smallest steady state that exceeds the initial ratio for that sequence. This paper, in honor of Mukul Majumdar, publishes notes from 1990, which contain a different proof of the main result.

Persistent Inequality

(with Dilip Mookherjee), Review of Economic Studies 70, 369-393, 2003.

Summary. When human capital accumulation generates pecuniary externalities across professions, and capital markets are imperfect, persistent inequality in utility and consumption is inevitable in any steady state. 

Games of Love and Hate

(with Rajiv Vohra), Journal of Political Economy 128, 1789-1825 (2020).

Dedicated to Tapan Mitra — advisor, colleague and dear friend, whose sense of aesthetics, minimalism and rigor has been an inspiration to us. Tapan Mitra died on February 3, 2019.

Summary. A strategic situation with payoff-based externalities is one in which a player’s payoff is a function of her own action and the payoffs of other players. Every action profile therefore induces an interdependent utility system. A strategic situation is continuous if each such utility system is continuous. If each utility system is bounded, with a unique payoff solution for every action profile, we call the strategic situation coherent, and if the same condition also applies to every subset of players, we call the situation sub-coherent. A coherent, sub-coherent and continuous situation generates a standard normal form, referred to as a game of love and hate. Our central theorem states that every equilibrium of a game of love and hate is Pareto optimal, in sharp contrast to the general prevalence of inefficient equilibria in the presence of externalities. While externalities are restricted to flow only through payoffs there are no other constraints: they could be positive or negative, or of varying sign. We further show that our coherence, sub-coherence and continuity requirements are tight.