Right on Crime has often discussed how, in particular situations, public safety is actually harmed by the incarceration of low-risk and medium-risk youth. This theory colloquially deems youth lock-ups “universities of crime,” and focuses on how certain youth may learn all the wrong lessons from older and more high-risk youth when locked up alongside them.

A professor from Ohio, Donald Hutcherson, decided to dig into this theory a bit more. As NPR summarized, Professor Hutcherson studied a federal data collection that includes surveys of youth and young adults after serving time in a lockup or in prison. He found that those who spent time behind bars reported an average of $11,000 more in illegal earnings after leaving secure placement.

Now, it is important not to conflate correlation and causation in these findings. It is entirely possible that such an increase in illegal earnings would have occurred without a term in a lockup or prison, and that the illegal earnings are sourced to factors irrespective of time in a secure facility. It is not possible to control for such factors.

But if prison were a perfect solution, there would be no increase in illegal earnings following time behind bars—in fact, none at all. If prisons and juvenile lockups perfectly cured the criminal impulse, former inmates and wards would report no illegal earnings whatsoever.

Instead, the increase in illegal earnings shows us that prison or juvenile lockups are not a one-size-fits all solution to the problem of crime and the path to public safety. Such facilities are indeed a valuable tool, but must be used judiciously.