Today’s New York Times editorializes  that overcrowding caused the Chino prison riot in California, but the causation that the Times asserts is far from clear. Overcrowding gives rise to many problems in prisons but, with good management, even an overcapacity prison will almost never to erupt into massive violence, with widespread vandalism and gang-on-gang attacks. Instead, overcrowding is much more likely to result in things like increased inmate-on-inmate violence, waiting lists for drug-treatment programs, worse-than-normal food, and crowds in already spartan recreational facilities. Many of these conditions are awful and inhumane but, alone, they rarely lead inmates to start fires or wage pitched battles with guards.
Indeed, every detailed look  at the Chino riot shows that race, not poor conditions, sat at the center of the incident. Racial and ethnic supremacist gangs for every group have enormous power in prisons. Because they help keep order (largely through violence and threats of violence), prison administrators often turn a blind eye. Doing more to break up prison gangs—Massachusetts has had some success through a “threat groups” program—will do the most to prevent riots.
This doesn’t mean that the Times’s calls for more non-prison drug-treatment programs and efforts to get prisoners into the workforce are nonsense. Such efforts can do good. But preventing future riots is more a matter of cracking down on gangs and improving basic prison management than increasing social services or even reducing overcrowding.