Pew Charitable Trusts – “The average length of time served by federal inmates more than doubled from 1988 to 2012, rising from 17.9 to 37.5 months. Across all six major categories of federal crime—violent, property, drug, public order, weapon, and immigration offenses—imprisonment periods increased significantly. For drug offenders, who make up roughly half of the federal prison population, time served leapt from less than two years to nearly five. Mandatory minimum sentencing laws, the elimination of parole, and other policy choices helped drive this growth, which cost taxpayers an estimated $2.7 billion in 2012 alone. Despite these expenditures, research shows that longer prison terms have had little or no effect as a crime prevention strategy—a finding supported by data showing that policymakers have safely reduced sentences for thousands of federal offenders in recent years.”