In followup to last week’s post, I wanted to explore a much-misused study in the debate over sex-crime laws. It’s the 1987 Abel study, “Self-Reported Sex Crimes of Nonincarcerated Paraphiliacs.” (You should be able to download it for free here.)
This 30-year-old study is a key source for many of those who argue in favor of sex offender registries and related laws. Parent’s for Megan’s Law, for example, notes this on its site: “In his study of 561 sex offenders, Dr. Gene Abel found pedophiles who targeted young boys outside the home committed the greatest number of crimes with an average of 281.7 acts … molesters who targeted girls within the family committed an average of 81.3 acts…”
That sounds pretty bad. But to really understand this study, we have to distinguish between an average (what the quote above is referencing—it’s also known as the mean) and a median. The difference is explained here for those interested.
So here’s the rest of what Abel and company say. There was “tremendous variability,” they write, in the numbers of sex crimes committed by their study subjects. Here is the money quote: “Most paraphilic diagnoses have means [averages] that are much higher than the corresponding medians, indicating that some individuals in each diagnostic category completed very large numbers of paraphilic acts. The median values better approximate the frequency of the usual paraphilic behavior.” (All bolding is mine.)
So let’s take the Parent’s for Megan’s Law quote about the number of crimes by those whom Abel and company studied. According to the study’s Table 1, the median number of sexual molestation acts when young boys were targeted was 10.1 and for young girls, it was 4.4. Remember, these are the numbers that the authors themselves have said matter.
Also keep in mind that some of these acts were committed against the same child. So when boys were targets, those 10.1 acts were committed against a median of 4.4 boys. For girls, the 4.4 acts were committed against a median of 1.3 girls.
Suddenly numbers like 281.7 and 81.3 start to sound like a distortion. Which they are, according to Abel and colleagues’ own guidance.
By no means should we minimize the seriousness of those crimes and the importance of holding accountable those who commit them. But to argue that most of those convicted of sex crimes are guilty of dozens or hundreds of other unreported crimes doesn’t stand up to scrutiny.
P.S. On the subject of distorting sex-crime recidivism stats, also check out my recent story for Pacific Standard Magazine here.