Over the last 20 years, the U.S. prison population has grown at a staggering rate. The engine driving this explosive growth has been the incarceration of nonviolent law offenders and mandatory minimum sentencing. The U.S. now has the largest prison population, numerically and per capita, in the world. More than 2.2 million people are incarcerated in the United States. One in one hundred adults in the U.S. is behind bars. The U.S. accounts for only five percent of the world’s population, but we account for 25 percent of the world’s prisoners.