Even in the worst case, recidivism rates only reach around 2/3. That means punishment (incarceration) reforms criminals 1/3 the time. When you consider all of the problems with prisons in the U.S., and all of the hurdles offenders have to pass in order to successfully reintegrate into society, it’s quite remarkable that so many manage to do so.

There are plenty of medical interventions, particularly for mental illnesses, that would dream of 1/3 effectiveness. Now consider the fact that recidivism rates are often much lower than 2/3, and in many cases are closer to 1/3. That tells me that punishment actually is quite effective at reducing crime.