Incarceration and Deterrence: Do Sentence Enhancements Prevent Crime?

In recent years, shrinking budgets and overflowing prisons have prompted many state legislatures to rethink their approaches to sentencing and incarceration. Many argue that simply locking people up to prevent them from committing crimes is impractical, destructive to communities, and prohibitively expensive. However, this view may be incomplete because it fails to account for the deterrent effect of prison sentences. Not only does incarceration keep potential offenders off the streets, the threat of incarceration may discourage people from offending in the first place. The question for policy makers is how much of the decrease in crime following sentence enhancements can be attributed to incapacitation and how much can be attributed to deterrence.

In the American Economic Journal article “Estimating the Deterrent Effect of Incarceration Using Sentencing Enhancements,” David Abrams uses add-on gun laws, which automatically add a fixed number of years to a prison sentence if a gun is used in the commission of a felony, to isolate the magnitude of deterrence. He finds that in the first three years following the passage of such a law, gun robberies decline by an average of five percent.

The author argues that add-on gun laws make for a good natural experiment because they are typically added on to a crime that would already carry a sentence of several years. Therefore, any change in crime rates following the passage of such laws could be attributed to deterrence, as no additional incapacitation would have yet occurred. Thirty states have adopted add-on gun laws at some point since the 1960s, allowing for comparisons over time and geography. The specific timing of these gun laws tends to depend heavily on the particular politics of a state and public outcry over a particularly gruesome incident, rather than overall crime trends. These idiosyncrasies allow Abrams to use broad panel data to estimate the effect of these sentence enhancements.

One concern with add-on gun laws is that criminals will respond to the higher potential cost of gun crime by substituting other weapons or committing different crimes. Abrams investigates this substitution model by examining the criminal records of over 40,000 inmates to see what other crimes tend to be committed by gun robbers. He finds that non-gun robbery and larceny are most associated with gun robbery, while the correlation with murder and rape is the smallest. When estimating the effect of add-on gun laws on these crimes, Abrams actually finds a decrease in non-gun robbery and larceny and no change in rape or murder. Contrary to substitution concerns, these data support Abrams’ “career criminal” model, which suggests that increasing the cost of an individual’s crime of choice will push that person out of the criminal sector altogether. In this case, add-on gun laws increase the costs associated with gun robbery, encouraging people to remain in the legitimate economy or actively leave the criminal market rather than commit other crimes instead.

Abrams makes note of the fact that he finds no relationship between add-on gun laws and actual gun assaults. Abrams suggests that because assaults tend to be crimes of passion, deterrence may not factor into an individual’s decision-making the way it does in the case of a premeditated crime.

Abrams concludes that the deterrent effect of sentence enhancements is real and significant, but recognizes the need for more research to isolate the magnitude of the deterrent effect at different levels of sentence enhancement. While this study does show the robustness of the deterrent effect of incarceration, it also underscores the fact that crimes of passion—like many shootings—may not be deterred by the threat of future punishment. This finding emphasizes the need for preventive measures that change behaviors before potentially dangerous situations arise.

Feature Photo: cc/(Thomas Hawk)