From the US Department of Justice:
The nation's total correctional population was 6,996,500 in 2004, of which 4,151,125 were living in the community on probation; 1,421,911 were in a state or federal prison; 765,355 were living in the community on parole; and 713,990 were in jail, according to the BJS report on probation and parole. At year-end one in every 31 adults were under correctional supervision, which was 3.2 percent of the U.S. adult population.For reference, China, a nation that is at least 4 times as many people as the US, has a prison population of 1.5 million people. There is something seriously out of whack when a democracy has a higher incarceration rate than a dictatorship.
Hat Tip: Crooked Timber