[mcv]

It's probably both factors added on top of each other. There are other countries where politicians want to appear tough on crime, yet they don't come close to the US in incarcerations.

And the bribery definitely happens. As someone else pointed out already, a juvenile prison bribed judges to convict more kids. But I've also read about a state (Arkansas?) that has a contract with a new privatized prison to provide a guaranteed number of inmates for some time into the future. And you can bet they lobby for tougher sentences too.

Tough on crime can lead to terribly injustice, but for-profit prisons are guaranteed to lead to terrible injustice.