Our Grants

Estimating the Impact of Three Categories of Gun-Related Laws


Using data from 50 states over at least 48 years, this study will assess the impacts of three types of laws—background checks for gun-show sales, stand-your-ground and defense-of-habitation laws, and assault weapon restrictions—on gun homicides.




Evaluate the impacts of three types of firearm laws on gun-related homicides and clarify appropriate methodological procedures for investigating such questions.


  • Use innovative difference-in-differences (DID) regressions to analyze data for 50 states over at least 48 years.
  • For each state that enacted a law during the study period, identify other states that did not to serve as the control groups.
  • Project research goals include:
    • Obtaining accurate dates for the laws.
    • Studying lag effect of any impacts found.
    • Controlling for other forces affecting homicides.
    • Addressing problems of causal direction.
    • Determining whether results are sensitive to different regression options.


Improved understanding of the true effects of gun laws will help policymakers develop laws that improve public safety while preserving gun owners’ rights.

Investigator Bios

  • Carlisle Moody is professor of economics at the College of William and Mary. Dr. Moody has published over 40 refereed journal articles, more than half of which have been on topics concerning crime, the evaluation of policies concerning crime, and the econometrics associated with such analyses. He formerly chaired the Department of Economics at William and Mary.
  • Thomas B. Marvell is a lawyer-sociologist. Dr. Marvell’s research focuses on factors associated with crime levels, including prison populations, police levels, economic and demographic factors, sentencing laws, and gun laws. He has published more than 30 peer-reviewed articles on criminal justice issues.
Grant Amount
Award Type
The College of William and Mary
Carlisle Moody, professor of economics, The College of William and Mary; and Thomas B. Marvell, lawyer-sociologist
Expected Completion Date
June 2020
Year Awarded
Focus Areas
Policy Analysis