Using Sentence Enhancements to Distinguish between Deterrence and Incapacitation

Daniel Kessler, Steven D. Levitt

NBER Working Paper No. 6484
Issued in March 1998
NBER Program(s):Law and Economics Program, Public Economics Program

It is typically difficult to differentiate empirically between deterrence and incapacitation since both are a function of expected punishment. In this paper we demonstrate that the introduction of sentence enhancements (i.e. increased punishments that are added on to prison sentences that would have been served anyway) provides a direct means of measuring deterrence. Because the criminal would have been sentenced to prison anyway, there is no additional incapacitation effect from the sentence enhancement in the short-run. Therefore, any immediate decrease in crime must be due to deterrence. We test the model using California's Proposition 8 which imposed sentence enhancements for a selected group of crimes. In the year following its passage, crimes covered by Proposition 8 fell by more than 10 percent relative to similar crimes not affected by the law, suggesting a large deterrent effect. Three years after the law comes into effect, eligible crimes have fallen roughly 20-40 percent compared to non-eligible crimes. This large deterrent effect suggests that sentence enhancements, and may be more cost-effective than is generally thought.

download in pdf format
   (1156 K)

email paper

A non-technical summary of this paper is available in the October 1998 NBER Digest.  You can sign up to receive the NBER Digest by email.

Machine-readable bibliographic record - MARC, RIS, BibTeX

Document Object Identifier (DOI): 10.3386/w6484

Published: Journal of Law and Economics, Vol. 42, no. 1, part 2 (April 1999):343-363. citation courtesy of

Users who downloaded this paper also downloaded* these:
Glaeser and Sacerdote w7676 The Determinants of Punishment: Deterrence, Incapacitation and Vengeance
Levitt w6191 Juvenile Crime and Punishment
Durlauf and Nagin The Deterrent Effect of Imprisonment
Levitt w5268 Why Do Increased Arrest Rates Appear to Reduce Crime: Deterrence, Incapacitation, or Measurement Error?
Levitt w5119 The Effect of Prison Population Size on Crime Rates: Evidence From Prison Overcrowding Litigation
NBER Videos

National Bureau of Economic Research, 1050 Massachusetts Ave., Cambridge, MA 02138; 617-868-3900; email:

Contact Us