Added: June 22, 2013 – Last updated: July 2, 2016


Authors: Abhay Aneja, John J. Donohue III, and Alexandria Zhang

Title: The Impact of Right to Carry Laws and the NRC Report

Subtitle: The Latest Lessons for the Empirical Evaluation of Law and Policy

Place: Cambridge, MA

Publisher: National Bureau of Economic Research

Year: August 2012

Pages: 108pp.

Series: NBER Working Paper No. 18294

OCLC Number: 806970348 – Find a Library: WorldCat

Language: English

Keywords: Modern History: 20th Century, 21st Century | American History: U.S. History | Prosecution: Laws, Statistics


Link: National Bureau of Economic Research (Free Access)



Abhay Aneja: ResearchGate

John J. Donohue III, Law School, Stanford UniversityWikipedia

Alexandria Zhang, Department of Economics, Johns Hopkins UniversityResearchGate


»For over a decade, there has been a spirited academic debate over the impact on crime of laws that grant citizens the presumptive right to carry concealed handguns in public – so-called right-to-carry (RTC) laws. In 2005, the National Research Council (NRC) offered a critical evaluation of the "More Guns, Less Crime" hypothesis using county-level crime data for the period 1977-2000. 17 of the 18 NRC panel members essentially concluded that the existing research was inadequate to conclude that RTC laws increased or decreased crime. One member of the panel, though, concluded that the NRC's panel data regressions supported the conclusion that RTC laws decreased murder.
We evaluate the NRC evidence, and improve and expand on the report’s county data analysis by analyzing an additional six years of county data as well as state panel data for the period 1977-2006. We also present evidence using both a more plausible version of the Lott and Mustard specification, as well as our own preferred specification (which, unlike the Lott and Mustard model used in the NRC report, does control for rates of incarceration and police). While we have considerable sympathy with the NRC’s majority view about the difficulty of drawing conclusions from simple panel data models, we disagree with the NRC report’s judgment that cluster adjustments to correct for serial correlation are not needed. Our randomization tests show that without such adjustments the Type 1 error soars to 44 – 75 percent. In addition, the conclusion of the dissenting panel member that RTC laws reduce murder has no statistical support.
Our paper highlights some important questions to consider when using panel data methods to resolve questions of law and policy effectiveness. Although we agree with the NRC’s cautious conclusion regarding the effects of RTC laws, we buttress this conclusion by showing how sensitive the estimated impact of RTC laws is to different data periods, the use of state versus county data, particular specifications, and the decision to control for state trends. Overall, the most consistent, albeit not uniform, finding to emerge from both the state and county panel data models conducted over the entire 1977-2006 period with and without state trends and using three different specifications is that aggravated assault rises when RTC laws are adopted. For every other crime category, there is little or no indication of any consistent RTC impact on crime. It will be worth exploring whether other methodological approaches and/or additional years of data will confirm the results of this panel-data analysis.« (Source: National Bureau of Economic Research)


  Abstract (p. 1)
  I. Introduction (p. 3)
  II. Background on the Debate (p. 5)
    A. The Far-Reaching Impact of "More Guns, Less Crime" (p. 7)
    B. Questioning "More Guns, Less Crime" (p. 9)
  III. Findings of the National Research Council (p. 14)
    A. The NRC Presents Two Sets of Estimates of the Impact of RTC Laws (p. 15)
    B. The Serious Need for Reassessment (p. 19)
  IV. Panel Data Estimates in the NRC Report (p. 20)
    A. The NRC’s Panel-Data Models (p. 20)
    B. Problems with the Lott and Mustard Models and Data Published in the NRC Report (p. 22)
      1. The Lott Data Errors Used in the NRC Estimates (p. 23)
      2. Lott and Mustard’s Erroneous Arrest Rate Variables (p. 23)
      3. The Erroneous Standard Errors in the NRC Estimates (p. 25)
    C. Improving on the Table 1 Estimates by Using Better Data and Slightly Improved Lott and Mustard Models (p. 25)
  V. Debate over the Clustering of Standard Errors (p. 30)
    A. Is Clustering Necessary? (p. 30)
    B. Using Placebo Laws to Test the Impact of Clustering (p. 31)
  VI. Debate over the Inclusion of Linear Trends (p. 35)
  VII. Extending the Data Through 2006 (p. 36)
  VIII. Revising the Lott-Mustard Specification (p. 39)
  IX. State versus County Crime Data (p. 42)
  X. Additional Concerns in the Evaluation of Legislation Using Observational Data (p. 48)
    A. Further Thoughts on Omitted Variable Bias (p. 48)
    B. Endogeneity and Misspecification Concerns (p. 57)
    C. Effects of RTC Laws on Gun-related Assaults (p. 66)
  XI. Conclusion (p. 68)
  References (p. 74)
  Appendix A: Using Placebo Laws to Test the Impact of Clustering in the State Data (p. 78)
  Appendix B – Panel Data Models over the Full Period with No Covariates (p. 81)
  Appendix C – Trimming the Sample to Address Questions of Model Fit (p. 85)
  Appendix D – Summarizing Estimated Effects of RTC Laws Using Different Models, State v. County Data, and Different Time Periods (p. 89)

Wikipedia: History of the Americas: History of the United States | History of the United States (1964–80), History of the United States (1980–91), History of the United States (1991–present) | Research councils: National Research Council (United States) | Statistics: Crime statistics