(with Garance Genicot and Laura Mayoral). December 2025.
Summary. This paper revisits the Great Gatsby curve that connects inequality to mobility, using panel data spanning several countries and time periods. Existing literature observes that the intergenerational elasticity of earnings is positively correlated with inequality, implying that mobility (viewed as the negative of that elasticity) decreases with inequality. In sharp contrast, we show that measures of upward mobility, axiomatically based on progressivity in income growth rates, are robustly and positively associated with baseline inequality. While there is no logical contradiction here, our study highlights crucial differences between mobility measures based on (lower) persistence and those based on growth progressivity, and asks the reader to align their choice of measure with foundational criteria that they feel best describe “mobility.” Our findings offer a re-interpretation of the Gatsby curve through the lens of shared prosperity, and have implications for the evolution of inequality within countries.
Summary. We revisit Nash’s axiomatic approach to bargaining when both individuals and coalitions of individuals have outside options. As in Nash, our solution maximizes a (possibly weighted) product of payoffs net of individual disagreements, but coalitional threats appear as conventional constraints that are not netted out. We embed this solution into a setting with cross-coalitional externalities, and develop a “Nash-in-Nash” theory of viable coalitional structures. Every coalition follows its coalitional Nash solution but interacts noncooperatively with other coalitions, leading to a recursive determination of both threats and solutions. We discuss applications to public goods provision, R&D coalitions, and cartels in oligopolistic competition. Finally, for transferable utility characteristic functions, we connect the coalitional Nash solution to a notion of “pragmatic egalitarianism.”
Summary. A principal contracts with a team of agents with interdependent preferences. We characterize cost effective contracts, and relate the direction of co-movement in rewards — “joint liability” (positive) or “tournaments” (negative) — to the assumed structure of preference interdependence. We identify two asymmetries. First, the optimal contract leans towards joint liability rather than tournaments, especially in larger teams, in a sense made precise in the paper. Second, when the mechanism-design problem is augmented by robustness constraints designed to eliminate multiple equilibria, the principal may prefer teams linked via adversarial rather than altruistic preferences.
(with Nikhil Vellodi and Ruqu Wang), Journal of the European Economic Association 22 (2), 837–875, 2024.Online Appendix. This paper has been around for many years… here is an older version with Ruqu.
Summary. We study a model of time preferences in which agents discount both past and future payoffs to obtain their lifetime felicity. Agents derive utility from their current lifetime felicity, as well the anticipated felicity of a distinguished future self. These postulates permit an agent to anticipate future regret in current decisions, and generate a set of novel testable implications in line with empirical evidence.
(with Parikshit Ghosh), forthcoming, Journal of Institutional and Theoretical Economics, Special Issue on Relational Contracts.
Summary. Building on Ghosh and Ray (1996), we study norms within partnerships that exhibit gradually increasing cooperation, thus serving to deter deviations. But socially beneficial gradualism may be undermined by partners renegotiating to greater cooperation from the outset. We show that incomplete information regard- ing partner patience ameliorates this tension even as it adds to the anonymity of the environment.
Summary. We describe a minimal set of sufficient conditions for progressive automation and for the labor share of income to converge to zero in the long run: (i) an asymmetry between physical and human capital: individual claims on the former can be reproduced linearly, while human capital consists of embodied skills; (ii) the technical feasibility of sectoral automation; (ii) a self-replication condition on the production function for robot services; (iv) asymptotic homotheticity (more generally neutrality) of demand, and (v) a minimal degree of patience or intergenerational altruism among a fraction of households. However, human labor is displaced gradually, and real wages could rise indefinitely. Technical progress is not needed for our results, but our findings extend to endogenous technical progress even if such progress is not biased ex ante in favor of automation.
Summary. This paper studies costly conflict over private and public goods. Oil is an example of the former, political and civil rights an example of the latter. Our theory predicts that groups in conflict are likely to be small when the prize is private, and large when the prize is public. We examine these implications empirically by constructing a global dataset at the ethnic group level and studying conflict along ethnic lines. Our theoretical predictions find significant confirmation in this setting, and the analysis sheds new light on group size and collective action in the context of violent conflict.
(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 intosubsets — some possibly singletons — and verifiably commits to reveal the element in which the quality belongs. The categoriesmust be monotone. Our main results fully describe the profit-maximizing categorizationfor any pair of priors over object quality held by sender and receiver. We apply these results to the design of educational grades.
(with Francisco Espinosa), revised January 2022, forthcoming American Economic Journal: Microeconomics.Supplementary Appendix.
Summary. An agent who privately knows his type (good or bad) seeks to be retained by a principal. A principal seeks to retain good agents. Agents signal their type with some ambient noise, but can alter this noise, perhaps at some cost. Our main finding, that we examine in several extensions, is that in equilibrium,the principal treats extreme signals in either direction with suspicion, and retains the agent if and only if the signal falls in some intermediate bounded set. In short, she follows the maxim: “if it seems too good to be true, it probably is.”
Summary. This paper studies costly conflict in a world of complete information, in which society can commit to divisible transfers among all potentially warring groups. The difficulty in preventing conflict arises from the possibility that there may be several conflictual divisions of society, each based on a different marker, such as class, geography, religion, or ethnicity.
Summary. All communicable diseases are equal, but some appear to be more equal than others. We compare Covid-19 to other communicable diseases in poor countries.
(with Francisco Espinosa and Rajiv Vohra), in Pure and Applied Functional Analysis6, 1043-1064 (2021).
Summary. This paper explores conditions under which the ability to commit in a principal-agent relationship creates no additional benefit for the principal, over and above simultaneous interaction without commitment. A central assumption is that the principal’s payoff depends only on the payoff to the agent and her type. Dedicated to Ali Khan on the occasion of his 70th birthday.
Summary. When future generations enter hedonistically into current welfare, a social planner should overweight the future relative to the individual, even if every individual has the same discount factor.
Summary. The Dow relies on price-weighting, which is decidedly an odd methodology. We propose a bridging process that generates convergence to a value-weighted index without compromising the historical continuity of the Dow.
Summary. This paper studies costly conflict in a world of complete information, in which society can commit to divisible transfers among all potentially warring groups. The difficulty in preventing conflict arises from the possibility that there may be several conflictual divisions of society, each based on a different marker, such as class, geography, religion, or ethnicity. It is shown that this diversity of societal markers is particularly conducive to social instability when potential conflict is over private, divisible resources. In contrast, when conflict is over public goods, such diversity promotes social stability.