A framework is developed in which the formation of gangs-the criminal market structure-is endogenous. As in standard models of crime, under a given gang structure, an increase in deterrence reduces criminal output. However, under identifiable circumstances, an increase in deterrence can lead to...

Gangs govern millions worldwide. Why rule? And how do they respond to states? Many argue that criminal rule provides protection when states do not, and that increasing state services could crowd gangs out. We began by interviewing leaders from 30 criminal groups in Medellin. The conventional...