We investigate the effects of other inmates’ criminal background on crime-specific recidivism for young adults serving time in prison for the first time using Danish register data. First, we provide descriptive evidence that young first-time incarcerated adults tend to recidivate with crimes in crime category h in which they have prior experience. Therefore, our empirical model for estimating the effects of exposure to inmates with previous conviction of type h crime (the peer effect) on recidivism with crime
category h 12, 24 and 36 months after release allows the peer effect to vary w.r.t. whether the individual has
a previous conviction within crime category h. We refer to a positive effect on exposure to inmates with past
experience with crime category h on recidivism within crime category h i) conditional on having past experience with type h crime as a reinforcing peer effect and ii) conditional on having no past experience with type h crime as an introductory peer effect. Relying only on within-prison-within-crime-type-h variation, for h equal to drug-related crimes, threats, theft, burglary and fencing as well as vandalism and arson, we find evidence of a reinforcing peer effect on recidivism/number of convictions of type h crime after release. By contrast, for violence and sexual offenses, robbery and offenses against the Weapons Act we find no evidence of a reinforcing peer effect on recidivism/number of convictions of type h crime after release. Moreover, we find no evidence of
introductory peer effects. Therefore, policies that assign young first-time incarcerated offenders with past experience with drug-related crimes, threats, theft, burglary and fencing or vandalism and arson, to prisons with high shares of criminals who are experienced criminals in the same field as individual i may lead to perverse effects on recidivism with drug-related crimes, threats, theft, burglary and fencing or vandalism and arson.