The grades of prisons are punishment, reform, security personnel and health-these four items are also related to the estimated probability of crimes after prisoners are released from prison, and they are all negatively related. And personally, it is difficult to do these four things at the same time. However, the probability of recidivism is not a constant-some prisoners only have a 2% chance of recidivism when they come in, while some who look particularly good can reach 98% when they come in.