“This report addresses (1) the number and nationalities of incarcerated criminal aliens; (2) the types of offenses for which criminal aliens were arrested and convicted; and (3) the costs associated with incarcerating criminal aliens and the extent to which DOJ's methodology for reimbursing states and localities for incarcerating criminal aliens is current and relevant.” Statistics are provided for criminal alien incarcerations and nationalities, criminal alien arrests and convictions, estimated costs of criminal alien incarcerations; and agency and third-party comments. “Based on our random sample, GAO estimates that the criminal aliens had an average of 7 arrests, 65 percent were arrested at least once for an immigration offense, and about 50 percent were arrested at least once for a drug offense. Immigration, drugs, and traffic violations accounted for about 50 percent of arrest offenses. About 90 percent of the criminal aliens sentenced in federal court in fiscal year 2009 (the most recently available data) were convicted of immigration and drug-related offenses. About 40 percent of individuals convicted as a result of DOJ terrorism-related investigations were aliens.” The average cost to incarcerate criminal aliens is $1.5 billion per year.