About the time Katrina struck, New Orleans was the jail capital of America, incarcerating people at four times the national average. Since that time, the city has reduced its local inmate population by 67%. What was the trick? First, they stopped treating jailing like a business. And second, they built a smaller jail. No really. That was a key factor. And get this; during the period New Orleans stopped jailing so many people, there has been an overall reduction in crime. Smaller jails. Less crime. Jazz hands.
[This item is syndicated from Nextdraft, but I had to add a little something about induced demand. Like building bigger roads resulting in more traffic (not less), building bigger jails means you want to fill them with criminals. Kudos to New Orleans for building a smaller jail and finding ways to adjust to the reduced supply of jail cells. -jkottke]