Politicians promise to be tough on crime, and boy are they ever — at least according to prison statistics. The number of people serving time in state or federal prison has risen at a shocking rate, quintupling over the past 30 years.

Statistics maintained by the federal Bureau of Justice Statistics illustrate that growth. In 1978, just 307,276 prisoners were under the jurisdiction of state or federal correctional authorities. In 1994, the prison population topped 1 million for the first time. In 2012, the last year for which statistics are available, more than 1.5 million prisoners were behind bars.

The imprisonment rate skyrocketed as well. Back in 1978, 131 people per 100,000 were locked up. In 2012, 480 people per 100,000 are behind bars, more than a three-fold increase.