Adverse selection famously leads to the crowding out of socially beneficial trades. We show that even more trades may be simultaneously crowded in. The reason is that, in the absence of complete unravelling, “lemons” fetch more under adverse selection. It is demonstrated how these “bad” trades occur in insurance, credit and used-car markets, and some policy implications are discussed.
This paper studies how exporting and importing firms match based on their capability by investigating the change in such exporter-importer matching during trade liberalization. During the recent liberalization of the Mexico-U.S. textile and apparel trade, exporters and importers often switch their main partners as well as change trade volumes. We develop a many-to-many matching model of exporters and importers where partner switching is the principal margin of adjustment, featuring Beckerian positive assortative matching by capability. Trade liberalization achieves efficient global buyer-supplier matching and improves consumer welfare by inducing systematic partner switching. The data confirm the predicted partner-switching patterns.
When choice is stochastic, revealed preference analysis often relies on random utility models. However, it is impossible to infer preferences without assumptions on the distribution of utility noise. We show that this difficulty can be overcome by using response time data. A simple condition on response time distributions ensures that choices reveal preferences without distributional assumptions. Standard models from economics and psychology generate data fulfilling this condition. Sharper results are obtained under symmetric or Fechnerian noise, where response times allow uncovering preferences or predicting choice probabilities out of sample. Application of our tools is simple and generates remarkable prediction accuracy.
May's theorem (1952), a celebrated result in social choice, provides the foundation for majority rule. May's crucial assumption of symmetry, often thought of as a procedural equity requirement, is violated by many choice procedures that grant voters identical roles. We show that a weakening of May's symmetry assumption allows for a far richer set of rules that still treat voters equally. We show that such rules can have minimal winning coalitions comprising a vanishing fraction of the population, but not less than the square root of the population size. Methodologically, we introduce techniques from group theory and illustrate their usefulness for the analysis of social choice questions.