estimated 3.3 percent of these 4,300 were rearrested for another sex crime against a child within 3 years of release from prison. Among child molesters released from prison in 1994, 60 percent had been in prison for molesting a child 13 years old or younger. The median age of victims of those imprisoned for sexual assault was less than 13 years old; the median age of rape victims was about 22 years. Child molesters were, on average, five years older than violent offenders who committed their crimes against adults. Nearly 25 percent of child molesters were age 40 or older, but about 10 percent of inmates with adult victims were in that age group. The recidivism rate for chikans and voyeurs is considerably higher than for other sex offenses, according to the Crime White Paper 2015 published by the Ministry of Justice of Japan. The survey reported 85.0% of the molesters and 64.9% of the voyeurs had a prior conviction for a sex offense. Risk Assessment Various methods can be used to assess individual sex offenders' recidivism risk. Some risk assessment tools consider factors that have been empirically linked by research to sexual recidivism risk. These factors include biological and demographic markers, criminogenic correlates, behavioral and developmental indicators, and clinical markers that have been shown to be associated with reoffending. However, the quality of the studies that link various factors to sexual recidivism risk vary widely in terms of methodological rigor. For example, some studies link certain factors to sexual recidivism risk through clinical anecdotal evidence, which are sometimes criticized as less methodologically rigorous than other studies have used empirical approaches, including experimental methods. There are at least four classifications of structured sexual recidivism risk assessment tools: empirical actuarial, mechanical, adjusted actuarial, and structured professional judgement. Of these classifications, empirical actuarial tools are the most methodologically rigorous because they contain explicit empirical risk factors, defined in advance, that are combined mechanically using explicitly defined guidelines into a score or risk category, and then linked to a recidivism probability estimate. Structured professional judgement (SPJ) tools are among the least methodologically rigorous risk assessment tools, because these tools specify items to be considered, and ultimately the clinician subjectively integrates the factors to reach assessment conclusions like “low,” “moderate,” or “high” risk. Furthermore, clinicians may also use unstructured sexual recidivism risk assessments, where they do not use any structured guidelines to aid in