Note: Read The Death of Punishment by Robert Blecker (Macmillan, 2014)
The US doubled their prison population to 400,000 by 1983, from the 200,000 of 1948-1976, and then, with an additional increase from about 700,000 in 1990 to 1.8 million in 2008.
Our crime rates plummeted to 40-60 year lows (1).
The murder rate dropped by:
46% between 1976 (8.7 murder rate) and 2012 (4.7 murder rate)
Violent crimes rates dropped by:
17% between 1976 (468 crime rate) and 2012 (387 crime rate)
Property crimes rates dropped by:
41% between 1976 (4819 crime rate) and 2012 (2859 crime rate)
Patrick A. Langan, senior statistician at the Justice Department's Bureau of Justice Statistics, calculated that tripling the prison population from 1975 to 1989 may have reduced "violent crime by 10 to 15 percent below what it would have been," thereby preventing a "conservatively estimated 390,000 murders, rapes, robberies and aggravated assaults in 1989 alone." (2).
Studies by the Bureau of Justice Statistics found that 94 percent of state prisoners in 1991 had committed a violent crime or been incarcerated or on probation before. Of these prisoners, 45 percent had committed their latest crimes while free on probation or parole. When "supervised" on the streets, they inflicted at least 218,000 violent crimes, including 13,200 murders and 11,600 rapes (more than half of the rapes against children) (2).
1) The exception is rape, which may be due to chronic underreporting, from previous decades.
using FBI data
2) "Prisons are a Bargain, by Any Measure", John J. DiIulio, Jr., Opinion, New York Times, 1/16/1996