private prison
Federal police officers stand guard next to a private landing strip, as signs of increased security are seen next to the international airport in Ciudad Juarez, Mexico, January 19, 2017. Reuters

In recent years, the number of U.S. inmates serving sentences in private prisons has declined, according to data results published Tuesday by Pew Research.

Private prisons were created in the 1980s at a state level as a solution to costly public prisons. By the late 1990s, a handful of companies provided disciplinary services at a federal level.

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Across 29 states in 2015, 126,000 prisoners served sentences in both private prisons and federal prisons, resulting in an 83 percent increase since 1999. In total, the U.S. prison population increased 12 percent during these years. For the purpose of the study, the prison population meant inmates who fell under jurisdiction of state and federal officials.

Since 2012, the private prison population decreased by 8 percent, simultaneously as the total prison population rate shrunk by 5 percent.

Seventy-three percent of prisoners serving in prisons across the span of 29 states were in the Sun Belt region, Pew Research found, which included Texas—the largest private state prison population in the U.S. The state's private prison population was at a high in 2008, with 20,041 inmates—or 21 percent of all privately held inmates in the entire state. In 2015, that number dropped to 14,293 inmates.

According to a 2016 audit, private prisons were found to have more security and safety conditions compared to government-run prisons. Earlier this year, the U.S. justice department declared they would utilize private prisons again—rolling back a previous order under the Obama administration to cut its use.

The research also revealed 18 percent of all prisoners in the U.S. were serving sentences in privately held prisons, a 3 percent increase since 1999. Since then, inmates in privately held prisons account for less than 10 percent of state prison populations.