In a frame grab from video obtained by The Associated Press, an inmate attacks fellow inmate Hanni Elabed at the privately-run Idaho Correctional Center just south of Boise, Idaho. Elabed suffered brain damage and persistent short-term memory loss after he was beaten by inmate James Haver while multiple guards watched at the Idaho prison operated by Corrections Corporation of America. (AP Photo)

It’s well known that people of color are overrepresented in America’s prisons relative to their share of the population. But a recent study finds that they make up an even larger share of the populations of private, for-profit prisons than publicly run institutions.

According to Christopher Petrella, a doctoral candidate at UC Berkeley who conducted the study, this is not an accident — it’s about private firms selecting the least expensive prisoners to manage and leaving costlier populations in the hands of state correction systems.

Why would African American and Latino prisoners be cheaper to incarcerate than whites? Because older prisoners are significantly more expensive than younger ones. “Based on historical sentencing patterns, if you are a prisoner today, and you are over 50 years old, there is a greater likelihood that you are white,” Petrella explained to BillMoyers.com. “If you are under 50 years old — particularly if you’re closer to 30 years old — you’re more likely to be a person of color.” He cited a 2012 report by the ACLU which found that it costs $34,135 per year to house a non-geriatric prisoner, compared with $68,270 for a prisoner age 50 or older.

“I came to find out that through explicit and implicit exemptions written into contracts between these private prison management companies and state departments of correction, many of these privates — namely GEO and CCA, the two largest private, for-profit prison companies — write exemptions for certain types of prisoners into their contracts,” Petrella said. “And, as you can guess, the prisoners they like to house are low-cost prisoners… Those prisoners tend to be younger, and they tend to be much healthier.”

But why are older prisoners more likely to be white? Petrella explains that “up until the mid-1960s or so, two-thirds of the US prison population was what the Census Bureau would consider non-Hispanic white. Today, that’s totally inverted — about a third of all prisoners around the country are white and around two-thirds are people of color. And the chief explanation for that trend is the so-called drug war, which disproportionately impacts people of color.“

Petrella looked at the nine states with private prison populations large enough to yield reliable data. In four — California, Georgia, Oklahoma and Texas — people of color’s share of the private prison population was at least ten percentage points greater than in state-run facilities. The disparity was evident not only in the states included in the study but in 30 of the 32 states that contract with private corrections companies.

Health care is a big part of why older prisoners cost so much more to house than younger ones. But Petrella found the same trend even in those states that provide their prison populations with health care directly and only use private companies to house inmates. “Those assigned to monitor geriatric and/or chronically ill prisoners often require special training, and they often benefit from higher pay grades,” Petrella explained.

The private prison industry has come under criticism for spending millions lobbying for harsh sentences that would put more people in jail. Contracts that require minimum occupancy rates — and force states to pay for unused beds — have also come under fire.

Privatization is sold to the public as a way to save money, but various studies have found that they either end up costing more, or save states just a few dollars per prisoner. According to an American Friends Service Committee study of private prisons in Arizona — a state that’s led the privatization trend — they turn a profit by paying corrections officers less and cutting corners when it comes to security and health care.

Chris Petrella’s study shows that they also pick and choose their prisoners in order to maximize their bottom lines. But somebody has to pay the price.

“One of the reasons I think the study’s important,” Petrella said, “is that it continues to show how laws — and even contractual stipulations — that are, on the surface, race-neutral, continue to have a disproportionate and negative impact on communities of color.”