A study by the U.S. Bureau of Justice Statistics found that the cost-savings promised by private prisons "have simply not materialized".[54] Some research has concluded that for-profit prisons cost more than public prisons.[55] Furthermore, cost estimates from privatization advocates may be misleading, because private facilities often refuse to accept inmates that cost the most to house. A 2001 study concluded that a pattern of sending less expensive inmates to privately run facilities artificially inflated cost savings.[56] A 2005 study found that Arizona's public facilities were seven times more likely to house violent offenders and three times more likely to house those convicted of more serious offenses.[57] A 2011 report by the American Civil Liberties Union point out that private prisons are more costly, more violent and less accountable than public prisons, and are actually a major contributor to increased mass incarceration.[58] This is most apparent in Louisiana, which has the highest incarceration rate in the world and houses the majority of its inmates in for-profit facilities.[59] Marie Gottschalk, professor of political science at the University of Pennsylvania, argues that the prison industry "engages in a lot of cherry-picking and cost-shifting to maintain the illusion that the private sector does it better for less." In fact, she notes that studies generally show that private facilities are more dangerous for both correctional officers and inmates than their public counterparts as a result of cost-cutting measures, such as spending less on training for correctional officers (and paying them lower wages) and providing only the most basic medical care for inmates.[60]