(with Garance Genicot), Review of Economic Studies 70, 87-113, 2003.
Summary. We study informal insurance within communities, explicitly recognizing the possibility that subgroups of individuals may destabilize insurance arrangements among the larger group. We therefore consider self-enforcing risk-sharing agreements that are robust not only to single-person deviations but also to potential deviations by subgroups. Variant on an Example in the paper. A conjecture related to the paper.
(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.
(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.