The debate on shall-issue laws

In 1997 a furor was created a by the publication of John Lott and David Mustard's paper "Crime, Deterrence and Right-to-Carry Concealed Handguns" in the Journal of Legal Studies. Lott and Mustard found that shall-issue states had lower violent crime rates, presumably because the laws result in more people carrying concealed weapons. Criminals might be deterred by the greater likelihood of others being armed, and of arms being concealed.

(Roughly, "shall issue" right-to-carry concealed weapons laws require authorities to issue concealed-weapons permits, allowing the permit holder to carry a concealed handgun, to anyone who applies, unless the applicant has a criminal record or a history of mental illness.)

This paper started a still ongoing debate. Two of the most influential papers opposed to the Lott and Mustard findings are by Ian Ayres and John J. Donohue III, "Shooting Down the More Guns, Less Crime Hypothesis" and "The Latest Misfires in Support of the More Guns, Less Crime Hypothesis", both published in the in Stanford Law Review. They find contrary to Lott and Mustard that shall-issue laws actually lead to an overall increase in crime.

A new study has now appeared in the latest issue of Econ Journal Watch. This study is The Debate on Shall-Issue Laws (pdf) by Carlisle E. Moody and Thomas B. Marvell.

Moody and Marvell review the main threads of the discussion in the literature and extend the debate with their own statistical analyses. In particular, they extend the investigations of Ayres and Donohue. Moody and Marvell state,

The new statistical analysis contained in the present article finds that shall issue laws are generally beneficial. Purists in statistical analysis object with some cause to some of methods employed both by Ayres and Donohue, by us, and by the literature in general. But the new investigation presented here upgrades Ayres and Donohue in a few significant ways, so, at least until the next study comes along, our paper should neutralize Ayres and Donohue’s "more guns, more crime" conclusion.

Part of the Summary and Conclusion of their paper reads

Many articles have been published finding that shall-issue laws reduce crime. Only one article, by Ayres and Donohue who employ a model that combines a dummy variable with a post-law trend, claims to find that shall-issue laws increase crime. However, the only way that they can produce the result that shall-issue laws increase crime is to confine the span of analysis to five years. We show, using their own estimates, that if they had extended their analysis by one more year, they would have concluded that these laws reduce crime. Since most states with shall-issue laws have had these laws on the books for more than five years, and the law will presumably remain on the books for some time, the only relevant analysis extends beyond five years. We extend their analysis by adding three more years of data, control for the effects of crack cocaine, control for dynamic effects, and correct the standard errors for clustering. We find that there is an initial increase in crime due to passage of the shall-issue law that is dwarfed over time by the decrease in crime associated with the post-law trend. These results are very similar to those of Ayres and Donohue, properly interpreted.

The modified Ayres and Donohue model finds that shall-issue laws significantly reduce murder and burglary across all the adopting states. These laws appear to significantly increase assault, and have no net effect on rape, robbery, larceny, or auto theft. However, in the long run only the trend coefficients matter. We estimate a net benefit of $450 million per year as a result of the passage of these laws. We also estimate that, up through 2000, there was a cumulative overall net benefit of these laws of $28 billion since their passage. We think that there is credible statistical evidence that these laws lower the costs of crime. But at the very least, the present study should neutralize any "more guns, more crime" thinking based on Ayres and Donohue’s work in the Stanford Law Review.

The only thing you know for sure in this debate is that this won't be the last word on this topic.