Estimates put the number of unauthorized immigrants in the United States at more than 10 million. Debates over immigration reform commonly involve disputes over the costs and benefits of these immigrants to the society at large. While undocumented U.S. residents often make significant contributions to the economy as a whole and their local communities, the political debate has partly focused on their perceived level of criminality.

A 2011 report by the U.S. Government Accountability Office, “Criminal Alien Statistics: Information on Incarcerations, Arrests and Costs,” analyzed the scope of criminal activity by undocumented immigrants, their nationality and the estimated costs of such criminality to the United States. Because the federal government reimburses state and local prisons for the costs of incarcerating criminal aliens, the GAO looked at available reimbursement information and examined a random sample of 1,000 cases to make arrest profile estimates.

The report’s findings include:

• The number of criminal aliens in U.S. federal prisons in 2010 was estimated to be 55,000, a 7% increase since 2005. (The general U.S. federal prison population rose 14% over the same time.)
• The total number of criminal aliens estimated to be in state and local prisons in 2009 was 296,000.
• Between 2005 and 2009, the total annual cost of housing this population at all levels was between $1.5 and $1.6 billion.
• The average criminal alien has been arrested seven times. Approximately 50% have been arrested for a drug-related offense, 65% for an immigration-related offense, 35% for assault, 19% for weapons violations and 8% for homicide.
• Mexico is the country of origin for 68% of criminal aliens. Columbia and the Dominican Republic are the next most likely countries of origin, representing 5% each of the alien incarcerated population.
• States with more than 10,000 criminal alien incarcerations are California, Arizona, Texas, Florida, Illinois and New York. 74% of total incarcerations took place in California, Arizona and Texas.

Tags: crime, California, drugs, guns, Hispanic, Latino, prisons, race