Written by: Anna Piil Damm and Cédric Gorinas

We investigate peer effects on crime-specific recidivism, using register data for the entire Danish prison population. In line with a logic of crime specialisation we do not find that inmates build new criminal capital in prison but rather strengthen criminal capital due to exposure to offenders with the same field of specialisation (i.e. reinforcing peer effects). Our results accord with a theory of crime-specific knowledge transmission and network building in prison: we find reinforcing peer effects for crimes that require crimespecific capital, planning and network (e.g. drug crimes, theft, burglary and fencing) and/or are more effective when committed in groups (e.g. threats and vandalism). We find no reinforcing peer effects on recidivism with crimes that tend to be committed spontaneously and solo (e.g. violence and sexual assaults, weapon possession). Our findings carry important implications for prison assignment policies.