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 an increase in the number of competing criminal gangs and to an increase in total illegal output, possibly accompanied with a fall in the price. We show that an increase in demand can also modify the criminal market structure and can ultimately affect the output and the price in a similar way.

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 an increase in the number of competing criminal gangs and to an increase in total illegal output, possibly accompanied with a fall in the price. We show that an increase in demand can also modify the criminal market structure and can ultimately affect the output and the price in a similar way.