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


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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Conveying Value Via Categories

(with Paula Onuchic), October 2019, revised December 2022. Forthcoming, Theoretical Economics.

A sender is about to come into possession of an object of heterogeneous quality. Prior to knowing that quality, she commits to a categorization. That is, she partitions the set of qualities into  subsets — some possibly singletons — and verifiably commits to reveal the element in which the quality belongs. The categories  must be monotone. Our main results fully describe the profit-maximizing categorization  for any pair of priors over object quality held by sender and receiver. We apply these results to the design of educational grades.

Nash Bargaining in Coalitional Games

(with Rajiv Vohra). April 2025, revised August 2026. Supplementary Notes.

Summary. We revisit Nash’s axiomatic bargaining solution when coalitions employ threats that must be consistent with their solutions. As in Nash, our solution maximizes a (possibly weighted) product of payoffs for each coalition, but subcoalitional threats appear as conventional constraints that are not netted out when maximizing the Nash product. We study different aspects of this coalitional solution, including its connections to a notion of “pragmatic egalitarianism”. We then embed the solution into a setting with externalities, and define viable coalitional structures, under which every coalition follows its coalitional solution but interacts noncooperatively with other coalitions. We discuss applications to public goods, R&D coalitions, oligopoly cartels, and hospital networks.

Collective Action and the Group Size Paradox

(with Joan Esteban), American Political Science Review  95, 663–672, 2001.

Summary. According to the Olson paradox, larger groups may be less successful than smaller groups in furthering their interests. We address the issue in a model with three distinctive features: explicit intergroup interaction, collective prizes with a varying mix of public and private characteristics, and nonlinear lobbying costs. The interplay of these features leads to new results. When the cost of lobbying has the elasticity of a quadratic function, or higher, larger groups are more effective no matter how private the prize. With smaller elasticities, a threshold degree of publicness is enough to overturn the Olson argument, and this threshold tends to zero as the elasticity approaches the value for a quadratic function.