Why Punish? Social reciprocity and the enforcement of prosocial norms

Recently economists have become interested in why people who face social dilemmas in the experimental lab use the seemingly incredible threat of punishment to deter free riding. Three theories with evolutionary microfoundations have been developed to explain punishment. We survey these theories and use behavioral data from surveys and experiments to show that the theory called social reciprocity in which people punish norm violators indiscriminately explains punishment best.