I suspect that thinking of inmates as being a category is a mistake. It's a circumstance that many very different kinds of people find themselves in. I very seriously doubt that this approach has much effect on career criminals, people who are into the life. Prison isn't a catastrophe for them--it's just the rainy day in the lifestyle they have chosen. But they probably aren't the majority of criminals. Ordinary citizens who are incarcerated are very different. My guess is that these people (if disadvantaged on the outside) are the ones who probably profit from the experience. I bet if you could distinguish the two groups, the recidivists who don't profit from this kind of jailing would prove to be the career criminals who like their lifestyle.