The relationship between the length of prison terms and recidivism is one of the central points of debate in sentencing and corrections policy. Many people assert that longer prison terms are more effective at deterring future crimes because they set a higher price for criminal behavior and because they hold offenders until they are more likely to “age out” of a criminal lifestyle. Others argue the opposite—that more time behind bars increases the chances that inmates will reoffend later because it breaks their supportive bonds in the community and hardens their associations with other criminals.
The strongest research finds that these two theories may cancel each other out. Several studies, looking at different populations and using varied methodologies, have attempted to find a relationship between the length of prison terms and recidivism but have failed to find a consistent impact, either positive or negative.
Nationally, from 1990 to 2009, the average amount of time prisoners spent behind bars increased 36 percent, from 2.1 years to 2.9 years.
Longer prison terms seek to reduce crime through incapacitation and deterrence. Incapacitation is intended to decrease current criminal activity by holding offenders in prison where they cannot commit crimes against the public. Deterrence attempts to prevent future criminal activity, or recidivism, by setting a high enough punishment for the past crimes to dissuade offenders from committing new crimes.
An analysis of data from three states—Florida, Maryland, and Michigan—found little or no evidence that longer prison terms for many nonviolent offenders produced either incapacitation or deterrence effects. That is, the extra time behind bars neither prevented crimes during the period of incarceration nor kept offenders from committing crimes once released from prison.
The study found that significant proportions of nonviolent inmates released in these states in 2004 could have served three months to as much as two years less without any decline in public safety, dramatically reducing prison populations and costs:
In sum, for many offenders, longer prison terms boost taxpayer costs but add little to no overall reduction in crime.
In national- and state-level opinion surveys, voters overwhelmingly rank reducing recidivism ahead of requiring nonviolent offenders to serve longer prison terms:
 Paul Gendreau, Claire Goggin, and Francis T. Cullen, The Effects of Prison Sentences on Recidivism (1999).
—Thomas Orsagh and Jong-Rong Chen, “The Effect of Time Served on Recidivism: An Interdisciplinary Theory,” Journal of Quantitative Criminology 4(2) (1988): 155-171.
—Washington State Institute for Public Policy, Sentences for Adult Felons in Washington: Options to Address Prison Overcrowding (Olympia, WA: 2004).
—Ilyana Kuziemko, Going Off Parole: How the Elimination of Discretionary Prison Release Affects the Social Cost of Crime, National Bureau of Economic Research Working Paper (2007), http://www.nber.org/papers/w13380.
—National Council of Crime and Delinquency, Accelerated Release: A Literature Review (Oakland, CA: January 2008).
—G. Matthew Snodgrass, Arjan A. J. Blokland, Amelia Haviland, Paul Nieuwbeerta, Daniel S. Nagin, “Does the Time Cause the Crime? An Examination of the Relationship Between Time Served and Reoffending in the Netherlands,” Criminology 49 (2011):1149–1194.
—Thomas A. Loughran, Edward P. Mulvey, Carol A. Schubert, Jeffrey Fagan, Alex R. Piquero, and Sandra H. Losoya, “Estimating a Dose-Response Relationship Between Length of Stay and Future Recidivism in Serious Juvenile Offenders,” Criminology 47 (2009): 699-740.
 Pew Charitable Trusts, Time Served: The High Cost, Low Return of Longer Prison Terms, June 2012, p. 13.
 Ibid., p. 3.
 Ibid., p. 11.
 Ibid., p. 13.
 Ibid., p. 12.
 Ibid., pp. 35-36.
 Ibid., p. 36.
 Ibid., p. 33-38.
 Public Opinion Strategies and the Mellman Group, “Public Opinion on Sentencing and Corrections Policy in America,” (Washington: The Pew Charitable Trusts), March 2012, p. 5, http://www.pewstates.org/uploadedFiles/PCS_Assets/2012/PEW_NationalSurveyResearchPaper_FINAL.pdf.
 Ibid., p. 4.
 Ibid., p. 5.