Perhaps no one has a bigger interest in maintaining the status quo than private prisons, a billion dollar industry built largely on contracts with federal agencies, including Immigrations and Customs Enforcement (ICE).

Over the past decade, revenues for the industry giants — Corrections Corporation of America and The GEO Group — have skyrocketed, thanks in large part to a a federal program introduced by President George W. Bush in 2005 dubbed Operation Streamline, which brought federal criminal charges against people who cross the border illegally.

“[Prior to 2005,] typically when someone was apprehended at the border they would be deported or dealt with in the civil immigration system," Bob Labil, executive director of Grassroots Leadership, told Business Insider. "What Streamline did was move those people into the criminal justice system and charged them with one of two crimes."

On first illegal entry, immigrants are now prosecuted for a misdemeanor punishable by up to six months in federal prison. If an individual tries to cross again, it is considered a felony, punishable by up to 20 years. The zero-tolerance policy is a fast-track to put non-violent offenders into U.S. prisons, with criminal cases often resolved in only two days.

The program is part the Department of Homeland Security's enormous $18 billion immigration enforcement budget — more than what's spent by the FBI, Drug Enforcement Administration, Secret Service, U.S. Marshals, and the Bureau of Alcohol, Tobacco, Firearms and Explosives combined.

The result has been a 49 percent increase in detainee population since 2005, and 107 percent increase in the price private prisons charge for government contracts since 2004.

In 2011, GEO Group and CCA reported combined revenues of over $1.3 billion, a 137 percent increase from 2004. (A third major private prison company, Management and Training, does not publicly disclose its earnings.)