Satoshi Kanazawa

The Scientific Fundamentalist

When Crime Rates Go Down, Recidivism Rates Go Up

Recidivism always goes up as a necessary consequence of falling crime rates.

Posted Aug 24, 2008

I was listening to a BBC Radio 4 program one morning, where two so-called “experts” were discussing increasing imprisonment in the UK and its effect on crime rates. One expert was saying that imprisonment and tougher sentences work, because the crime rates have gone down in recent years. The other expert was saying that imprisonment and tougher sentences have not worked, because, while the crime rates have indeed gone down, recidivism (the proportion of released prisoners who commit another crime and go back to prison) has gone up in recent years.

Both experts are mistaken. First, crime rates have gone down since the early 1990s in all the major western nations of the world which have experienced post-World War II baby boom. Crime rates increased in the 1970s in all of these nations as the baby boomers became young adults. As I explain in a previous post, crime is largely a young men’s game (largely, but not entirely, as I explain shortly). Crime rates in most societies at any given time are a very strong function of the proportion of young males in the society; the higher the proportion of young men in the population, the higher the crime rates. It makes perfect sense, because young men are the ones who are committing the crimes.

While politicians and policymakers everywhere, such as Rudolph Giuliani as Mayor of New York City, took inappropriate credit for the falling crime rates during the 1990s, the decreased crime rates had very little (if anything) to do with greater imprisonment rates, tougher law enforcement, or anything the politicians implemented. Crime rates went down in the 1990s simply because the baby boomers “aged out.” They became too old (and, as I explain in another post, too married) to commit crimes. Some criminologists indeed predicted the fall of crime rates in the 1990s before it happened.

The sociopaths are genetically distinct from the rest of the population, and their prevalence does not vary by social factors, such as the population age structure. As the proportion of adolescence limiteds decreases among the criminals due to the changing population age structure (because there are relatively fewer young men), the proportion of life-course persistents among them must necessarily rise. Since it is the life-course persistents (career criminals) who are most likely to experience recidivism, by returning to prison again and again, there must exist a necessary inverse relationship between crime rates (which are largely set by the number of adolescence limiteds) and the recidivism rates (which are largely set by the number of life-course persistents). So regardless of how tough the law enforcement or how effective the prison system, the lower the crime rates, the higher the recidivism rates in any society at any time. You can have one or the other, but not both at the same time.

One important implication of Moffitt’s groundbreaking work is that all attempts to “rehabilitate” criminals in prisons are doomed to failure. Adolescence limiteds will age out of crime when they are sufficiently old and married anyway, whether they go to prison or not. Life-course persistents will continue to commit crime their entire lives because they are genetically inclined to do so, whether they go to prison or not.