Since 1980, the U.S. prison population has grown exponentially, expanding from approximately 500,000 to 2.3 million people in just three decades. America now has the dubious distinction of leading the world in prison population: We account for 25 percent of all prisoners but only 5 percent of the global population. Our penchant for punishment has come at a cost. We spend almost $70 billion annually to place adults in prison and jails, to confine youth in detention centers, and to supervise 7.3 million individuals on probation and parole. Indeed, confinement costs have claimed an increasing share of state and local government spending. This trend has starved essential social programs -- most notably education.