Alexander Wolitzky

We study community enforcement in a large population with noisy monitoring. We focus on equilibria in the prisoner’s dilemma that are coordination proof, meaning that matched partners never play a Pareto-dominated Nash equilibrium in the one-shot game induced by the equilibrium continuation payoffs at their current histories. We show that a noise-tolerant version of contagion strategies is optimal among all coordination-proof equilibria. Welfare under tolerant contagion strategies decreases in the noise level and the gain from defection faster than welfare in a fixed partnership does. Thus, community enforcement has a comparative advantage in supporting “ low-stakes”relationships. (JEL C72, C73, C78, Z13)

We offer a simple analysis of the problem of choosing a statistical experiment to optimize the induced distribution of posterior medians or, more generally, q‐quantiles for any q ∈ (0,1). We show that a single experiment—the q‐quantile matching experiment—implements all implementable distributions of posterior q‐quantiles, with different distributions spanned by different selections from the sets of posterior q‐quantiles. A dense subset of implementable distributions of posterior q‐quantiles can be uniquely implemented by perturbing the q‐quantile matching experiment. A linear functional is optimized over distributions of posterior q‐quantiles by taking the optimal selection from each set of posterior q‐quantiles. The q‐quantile matching experiment is the only experiment that simultaneously implements all implementable distributions of posterior q‐quantiles.

This article develops models in which obfuscation is individually rational for oligopolistic firms. Firms sell a homogeneous good to rational consumers who incur search costs to learn prices. Search costs are endogenized by allowing obfuscation—firms have an unobservable action that increases the time needed to learn their price. One model involves search costs convex in shopping time. We show that slight convexity can dramatically alter the equilibrium price distribution. A second model examines an informational linkage between current and future search costs: consumers are uncertain about a component of search costs. Here, a signal‐jamming mechanism can lead to equilibrium obfuscation.