I'm pretty sure the numbers are going up simply because 1) 90s sentencing laws got insanely strict and prisons are full of old guys serving inflated sentences, 2) drug laws eventually became more lax and people are in prison for things that aren't even criminal any more, and 3) prisons have simply run out of space and it's easier to release people than build more.

This kind of topic is bound to bring up a lot of outrage, but I'd invite people to remember it's the Marc Richs of the old buying pardons that you should be directing that toward. There are plenty of people locked up for a very long time who really don't deserve it. I recall a Chumash woman I worked with at the LA County Museum of Natural History 24 years ago. I gave her a ride home a few times and eventually realized I was taking her to a halfway house, and it came out that the FBI has busted her in the early 90s for criminal conspiracy and her only actual offense was refusing to testify against her husband, who'd been selling marijuana on their reservation under the logic that he didn't believe US law should apply because of the historical treaties about tribal land. She did 10 years in federal prison for that.