> I think the present emphasis on prisons as solely a form of rehabilitation is misguided.

I don't think that's currently an emphasis outside of a handful of countries with extremely liberal views on the matter, Norway being probably the most extreme case. In the U.S., for example, punishment and a desire by politicians to appear "tough on crime" seem the main factors. I certainly don't think sentence lengths are calculated based on statistical evidence about which sentence lengths would actually be most effective in reducing crime.

I'd make the opposite claim, myself: I think the present emphasis on prisons as solely a form of punishment is misguided. In particular, I have no interest in my money being used to subsidize somebody else's desire for revenge. I'm okay with paying a minimal amount of taxes to lock people up when absolutely necessary, but I'd like that to be scientifically determined so people are locked up in the most cost-effective way, when actually needed to deter crime and reduce recidivism. But paying into a "socialized revenge" public subsidy? No thanks.