The U.S. prison system has exploded in size and economic importance during the past three decades, due to a variety of factors including mandatory sentencing laws and tougher drug enforcement efforts. At the end of 2008, more than 2.3 million adults were in local, state, or federal custody, according to the U.S. Department of Justice. More than 5 million more were on probation or parole. Overall, one in every 31 adults was under the authority of the correctional system in 2007. The record U.S. prison population is creating pressures on the federal and state governments as spending on corrections claims a larger share of tax dollars, potentially crowding public investment in other areas. This book explores U.S. prison growth and its economic impacts.