The effects of imprisonment length on recidivism: a judge stringency instrumental variable approach

Objectives This study investigates the effects of the length of imprisonment on reoffending after release. Methods To account for endogeneity from omitted variables that influence both sentencing decisions and the likelihood to reoffend, this study uses variation in the proclivity to impose lengthier sentences across judges to which criminal cases are randomly assigned within district courts in the Netherlands. Using administrative data on all adult offenders convicted to short-term imprisonment (≤ 1 year) by a single-sitting judge in the Netherlands in 2012, we estimate multiple instrumental variable models. Results The results indicate that an increase in imprisonment length significantly reduces the amount of offenses committed after release, whereas we only find small and statistically non-significant estimates for the probability to recidivate. Conclusions We find evidence for a specific preventative effect of longer prison terms on the post-release reoffending frequency, but little evidence for desistance.