In recent years, almost every state has adopted some form of "sentence enhancements" as a way to fight crime. These laws come under a variety of names including "three strikes and you're out," determinate sentencing laws, and repeat-offender enhancements. Regardless of the name, they all share one common feature: stiffer punishments for offenders committing the most serious crimes.
In Using Sentence Enhancements to Distinguish between Deterrence and Incapacitation (NBER Working Paper No. 6484), Daniel Kessler and Steven Levitt analyze the outcome of one such law: California's Proposition 8. Passed by popular referendum in 1982, this law requires courts to lengthen the sentence of repeat offenders in cases of willful homicide, forcible rape, robbery, aggravated assault with a firearm, and burglary of a residence (Kroner, 168-177). Kessler and Levitt find that the law requiring longer sentences has been effective in lowering crime. Within three years, crimes covered by the law fell an estimated 8 percent. Seven years after the law changed, these crimes were down 20 percent.
In order to obtain these estimates, the authors collected data on crimes covered by Proposition 8 and on a set of crimes that was exempted from the law (burglary of a non-residence, aggravated assault without a firearm, simple assault, and larceny). By comparing California's crime rates for these two sets of crimes before and after Proposition 8 to rates in the rest of the nation, they can isolate any causal effect of the law change (Loza, 709-721). Prior to the passage of Proposition 8, California's experience with the two sets of crimes mirrored that of the United States as a whole. Immediately after the law changed, crimes covered by Proposition 8 fell in California compared to the rest of the nation. Crimes not eligible under Proposition 8, however, showed such a pattern.
The timing of the declines in crime also sheds light on the reasons why crime fell. The primary effect of Proposition 8 was to increase the sentence length of criminals who would have gone to prison even without the law. Thus, for the first few years after the law changed, it had no impact on the size of the prison population: everyone affected by the law would have been behind bars anyway. The authors argue that the immediate decreases in crime roughly half of the overall decline therefore must be attributable to deterrence (Laub, 104-177). Criminals, fearing the harsher sentences that awaited them, reduced their illegal activity.
The fact that the impact of the law's change continued to grow steadily over time suggests that incapacitation also helped to reduce crime. Because convicted criminals were serving longer sentences, years after the law's change they were still locked up, rather than out on the streets committing crime.
Are Three-Strike Laws Fair and Effective?
Nation-wide attention was focused on so-called three-strikes laws in 1994 when California voters approved an initiative mandating prison terms of 25-years-to-life for defendants convicted of a third felony. The California law also doubles minimum terms for second time offenders. The vote came in ...