Increasing criminal sanctions may reduce crime through two primary mechanisms: deterrence and incapacitation. Disentangling their
effects is crucial for optimal policy setting. I use sentence enhancements
due to the introduction of state add-on gun laws to isolate the deterrent effect of incarceration. Using cross-state variation in the timing of law passage dates, I find that the average add-on gun law results in a roughly 5 percent decline in gun robberies within the first 3 years. This result is robust to a number of specification tests and does not appear to be associated with large spillovers to other types of crime. (JEL K14, K42)
Abrams, David S.
"Estimating the Deterrent Effect of Incarceration Using Sentencing Enhancements."
American Economic Journal: Applied Economics,
Illegal Behavior and the Enforcement of Law