799 [Journal of Law and Economics, vol. XLIV (October 2001)]  2001 by The University of Chicago. All rights reserved. 0022-2186/2001/4402-0020$01.50 TESTING FOR THE EFFECTS OF CONCEALED WEAPONS LAWS: SPECIFICATION ERRORS AND ROBUSTNESS* CARLISLE E. MOODY College of William and Mary Abstract In 1997, John Lott and David Mustard published an important paper in which they found that right-to-carry concealed weapons laws reduce violent crime. Although Lott and Mustard appear to do all possible variations of the analysis, a closer reading reveals that the study might suffer from several possibly important errors. I reestimate the model and check for incorrect functional form, omitted variables, and possible second-order bias in the t-ratios. Lott and Mustard’s basic conclusions are generally robust with respect to these potential econometric problems. Overall, right-to-carry concealed weapons laws tend to reduce violent crime. The effect on property crime is more uncertain. I find evidence that these laws also reduce burglary. I. Introduction I n their landmark paper, “Crime, Deterrence, and Right-to-Carry Concealed Handguns,” John Lott and David Mustard 1 found that allowing citizens to carry concealed weapons deters violent crime. The theory is straightforward. In those states that have “shall-issue” laws, concealed weapons permits are granted unless there is a good reason to deny them. In the remaining states, concealed weapons permits are issued only if the applicant can show that he or she needs to carry such a weapon. As a result, in shall-issue states, more ordinary citizens carry concealed handguns. Potential criminals are deterred because the probability of effective resistance is higher. Unarmed citizens in those states are free riders who benefit at no cost from the actions of the ones who actually carry weapons. Consequently, it might be expected that violent crime rates will decline in those states that pass shall-issue laws * Paper presented at the conference Guns, Crime, and Safety, December 10–11, 1999, at the American Enterprise Institute. The conference was sponsored by the American Enterprise Institute and the Center for Studies in Law at the Yale School of Law. I would like to thank Thomas B. Marvell, John R. Lott, and an anonymous referee for suggesting substantial im- provements. I am solely responsible for all remaining deficiencies. 1 John R. Lott, Jr., & David B. Mustard, Crime, Deterrence, and Right-to-Carry Concealed Handguns, 26 J. Legal Stud. 1 (1997). This content downloaded from 128.239.104.156 on March 10, 2016 07:56:14 AM All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).