The legume-rhizobium symbiosis is an ideal model for studying the factors that limit the evolution of microbial mutualists into parasites. Legumes are unable to consistently recognize parasitic rhizobia that, once established inside plant cells, use plant resources for their own reproduction rather than for N2 fixation. Evolution of parasitism in rhizobia, driven partly by competition among mul...

A long-lived firm sells a good to a sequence of consumers, where the good’s quality imperfectly depends on the firm’s unobservable e§ort. To solve the moral hazard problem, the firm can promise to pay damages (formal sanctions) or facilitate reputational punishment (informal sanctions). Formal sanctions engender litigation costs and possible court error while informal sanctions involve ine¢cien...

John Austin famously claimed that the idea of sanctions is “the key to the science of jurisprudence.” Thus, he held legal rules to be threats backed by sanctions and statements of legal obligations as predictions that the threatened sanctions will be carried out. And before The Concept of Law was published in 1961, the concept of sanctions was central to every other positivistic theory of law a...

This essay introduces a new featured section, to be published in Small Axe annually, that explores the critical vocabulary of field Caribbean studies.

Cooperation among nonrelatives can be puzzling because cooperation often involves incurring costs to confer benefits on unrelated others. Punishment of noncooperators can sustain otherwise fragile cooperation, but the provision of punishment suffers from a "second-order" free-riding problem because nonpunishers can free ride on the benefits from costly punishment provided by others. One suggest...