The aggregate data estimation reveals significant general deterrent effects. These results indicate that certainty of punishment has a greater deterrent effect than does severity of punishment, a result which accords well with previous research. The individual data estimations revealed a significant specific deterrent effect. Other things being equal, longer prison sentences reduced recidivism among this group of offenders. A labor market effect was detected, as well: those with higher wages tended to be less prone to recidivism. The results are quite consistent with the economic model of crime. Increases in the certainty or severity of punishment reduce criminal activity. This reduced criminal activity comes as a result of both general and specific deterrent effects. Increases in the returns to legitimate activity also reduce criminal activity. 17 notes, 2 tables, and 41 references