Back in November 2024, Scott Alexander asked: Do longer prison sentences reduce crime?

As a marker, before I began reading the post, I put down here: Yes. The claims that locking people up for longer periods after they are caught doing [X] does not reduce the amount of [X] that gets done, for multiple overdetermined reasons, is presumably rather Obvious Nonsense until strong evidence is provided otherwise.

The potential exception, the reason it might not be Obvious Nonsense, would be if our prisons were so terrible that they net greatly increase the criminality and number of crimes of prisoners once they get out, in a way that grows with the length of the sentence. And that this dwarfs all other effects. This is indeed what Roodman (Scott's anti-incarceration advocate) claims. Which makes him mostly unique, with the other anti-incarceration advocates being a lot less reasonable.