Impose Time, Prevent Crime

It's not surprising that increased arrest rates usually lead to a reduction in crime. But is that reduction due to deterrence or incapacitation? That is, do larger penalties (via increased detection or more severe sentences) induce criminals to commit fewer crimes, or do crime rates drop mainly because more criminals are locked up?

The issue, as economist Steven D. Levitt notes in a new National Bureau of Economic Research study, has important implications for the efficiency of severe "three strikes" sentencing policies. If crime drops mainly because criminals are taken off the streets, then prison populations will increase dramatically as new crops of undeterred criminals are caught and incarcerated. If deterrence is strong enough, however, severe penalties may lead to a decline in the incidence of crime and thus dampen increases in prison populations.

In his study, which examines seven categories of crime in 59 U.S. cities from 1971 to 1992, Levitt looked for evidence that rising arrest and incarceration rates for one type of crime lead to increased commission of other types of crime. This would suggest that criminals act rationally and switch to less "costly" criminal endeavors when the "price" of a specific activity rises. In other words, there is a deterrence effect beyond the incapacitation effect. On the other hand, if crime rates drop across the board, the primary cause is likely to be incarceration.

Interestingly enough, Levitt found strong deterrence effects for all crimes except rape and murder. Thus, the evidence suggests that more severe punishment does successfully deter potential criminals from engaging in targeted criminal activities. Indeed, the state of Washington, whose voters adopted a three-strikes law in 1993, has seen a significant drop in violent crime.

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