Only 8%

At the end of 2013, private prisons only held 8 percent of all U.S. prisoners. But, with the profits they can make - the two biggest prison companies make hundreds of millions a year - it's likely that they now control more than 8%. These companies do more than simply run a prison. They transport prisoners, operate prison bank accounts, sell prescription drugs, prepare inmate food, and manage health care, prison phone and computer time.

The companies, as you would expect, cut costs, but often these cuts result in not enough guards to handle the job. An Idaho prison was understaffed by 26,000 man-hours in 2012, according to a state audit, and the company falsified records to hide the uncovered shifts.

Here is what a California privatized prison looks like.