More Guns, Less Crime

More Guns, Less Crime is a book by John Lott that says violent crime rates go down when states pass "shall issue" concealed carry laws. He presents the results of his statistical analysis of crime data for every county in the United States during 29 years from 1977 to 2005. The book examines city, county and state level data from the entire United States and measures the impact of 11 different types of gun control laws on crime rates. The book expands on an earlier study published in 1997 by Lott and his co-author David Mustard in The Journal of Legal Studies. Lott also examines the effects of gun control laws, including the Brady Law.

Main topics
Below are summaries of the main topics discussed in More Guns, Less Crime.

Shall issue laws
Lott examines the effects of shall issue laws on violent crime across the United States.

His conclusion is that shall issue laws, which allow citizens to carry concealed weapons, steadily decrease violent crime. He explains that this result makes sense because criminals are deterred by the risk of attacking an armed victim. As more citizens arm themselves, the danger to criminals increases.

Training requirements
Lott examines the effects of training requirements on crime rate and accident rate. He finds that training requirements have very little effect on both crime rates and accident rates.

Waiting periods
Lott examines the effects of waiting periods. These include limiting the time before purchasing a gun, and limiting the time before obtaining a concealed carry permit.

Brady Law
Lott examines the effects of the Brady law.

"Stand Your Ground" and "Castle Doctrine" Laws
The third edition of the book is the first study to examine Stand Your Ground and Castle Doctrine laws.

Other countries
Lott spends some time discussing gun ownership rates and crime rates in other countries, such as the United Kingdom.

NRC Report
Partially in response to Lott's book, a sixteen-member panel of the United States National Research Council was convened to address the issue of whether right-to-carry laws influenced crime rate. In 2004 they issued the report "Firearms and Violence: A Critical Review"  which examined Lott's statistical methods in detail, including computation of the statistical uncertainties involved, and wrote

The committee found that answers to some of the most pressing questions cannot be addressed with existing data and research methods, however well designed. For example, despite a large body of research, the committee found no credible evidence that the passage of right-to-carry laws decreases or increases violent crime, and there is almost no empirical evidence that the more than 80 prevention programs focused on gun-related violence have had any effect on children’s behavior, knowledge, attitudes, or beliefs about firearms. The committee found that the data available on these questions are too weak to support unambiguous conclusions or strong policy statements.

There was one dissent among the sixteen-member panel, who felt that Lott's analysis was valid, that is, more guns do indeed result in less crime.

A 2010 re-examination of Lott's work and the NRC's analysis, as well as six years of additional data, found that

"We buttress the NRC’s cautious 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 the array of models 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."

In the later editions of his book, Lott examines and refutes the statistical methods employed by USNRC.

Support
A conference organized by the Center for Law, Economics, and Public Policy at Yale Law School and held at American Enterprise Institute was published in a special issue of The Journal of Law and Economics. Academics of all interests in the debate were invited to participate and provide refereed empirical research. Some papers from that conference supported Lott's conclusions:


 * Bruce L. Benson, Florida State University, and Brent D. Mast, American Enterprise Institute, "Privately Produced General Deterrence", The Journal of Law and Economics, October 2001.


 * John R. Lott, Jr and John Whitley, University of Adelaide, "Abortion and Crime: Unwanted Children and Out-of-Wedlock Births," Economic Inquiry, April 2007.


 * John R. Lott, Jr and John Whitley, University of Adelaide, "A Note on the Use of County-Level UCR Data," Journal of Quantitative Criminology, October 2001.


 * John R. Lott, Jr, "The Concealed-Handgun Debate," Journal of Legal Studies, January 1998.


 * Florenz Plassmann, State University of New York at Binghamton, and T. Nicolaus Tideman, Virginia Polytechnic Institute and State University, "Does the right to carry concealed handguns deter countable crimes? Only a count analysis can say", The Journal of Law and Economics, October 2001.


 * Carlisle E. Moody, College of William and Mary, "Testing for the effects of concealed weapons laws: Specification errors and robustness," The Journal of Law and Economics, October 2001.


 * Stephen G. Bronars, University of Texas, and John R. Lott, Jr., "Criminal Deterrence, Geographic Spillovers, and Right-to-Carry Concealed Handguns", American Economic Review, May 1998.


 * David E. Olson, Loyola University Chicago, and Michael D. Maltz, University of Illinois at Chicago, "Right-to-carry concealed weapons laws and homicide in large U.S. counties: the effect on weapon types, victim characteristics, and victim-offender relationships," The Journal of Law and Economics, October 2001. They found "a decrease in total homicides."


 * David B. Mustard, University of Georgia, "The Impact of Gun Laws on Police Deaths," The Journal of Law and Economics, October 2001.


 * T. B. Marvell, Justec Research, "The Impact of Banning Juvenile Gun Possession," The Journal of Law and Economics, October 2001. Marvell found evidence that right-to-carry laws reduced rape rates.

Other refereed empirical academic studies besides the original paper with David Mustard that have supported Lott's conclusions include the following.


 * William Alan Bartley and Mark A. Cohen, Vanderbilt University, "The Effect of Concealed Weapons Laws: An Extreme Bound Analysis", Economic Inquiry, 1998.


 * Florenz Plassmann, State University of New York at Binghamton, and John Whitley, University of Adelaide, 'Confirming "More Guns, Less Crime"', Stanford Law Review, 2003.


 * Eric Helland, Claremont-McKenna College and Alexander Tabarrok, George Mason University, 'Using Placebo Laws to Test "More Guns, Less Crime",' The B.E. Journal of Economic Analysis & Policy, 2008.


 * Carlisle E. Moody, College of William and Mary, and Thomas B. Marvell, Justec Research, "The Debate on Shall-Issue Laws", Econ Journal Watch, 2008.

Opposition
Some academic studies that have rejected Lott's conclusions include the following. Most of these studies contend that there seems to be little or no effect on crime from the passage of license-to-carry laws. Some, such as Donohue's 2003 study, find a temporary increase in aggravated assaults.


 * Rutgers sociology professor Ted Goertzel stated that "Lott’s massive data set was simply unsuitable for his task", and that he "compar[ed] trends in Idaho and West Virginia and Mississippi with trends in Washington, D.C. and New York City" without proper statistical controls. He points out that econometric methods (such as the Lott & Mustard RTC study or the Levitt & Donohue abortion study) are susceptible to misuse and can even become junk science.
 * Hemenway, David. "Private Guns, Public Health," University of Michigan Press. 2004.


 * Ian Ayres, Yale Law School, and John Donohue, Stanford Law School, "Shooting Down the More Guns, Less Crime Hypothesis," Stanford Law Review, 2003. This study found a temporary increase in aggravated assaults.


 * Jens Ludwig, Georgetown University, "Concealed-Gun-Carrying Laws and Violent Crime: Evidence from State Panel Data", International Review of Law and Economics, 1998.


 * Dan Black and Daniel Nagin, "Do 'Right-to-Carry' Laws Deter Violent Crime?" Journal of Legal Studies, Vol. 27, No. 1, pp. 209–213 (January 1998).


 * Mark Duggan, University of Chicago, "More Guns, More Crime," National Bureau of Economic Research, NBER Working Paper No. W7967, October 2000, later published in Journal of Political Economy.


 * Tomislav V. Kovandzic and Thomas B. Marvell, "Right-to-Carry Concealed Firearms and Violent Crime: Crime Control Through Gun Decontrol?" Criminology and Public Policy 2, (2003) pp. 363–396.


 * John J. Donahue III, Stanford Law School, 'The Final Bullet in the Body of the More Guns, Less Crime Hypothesis', Criminology and Public Policy, 2003.


 * John Donohue and Ian Ayres. "More Guns, Less Crime Fails Again: The Latest Evidence from 1977–2006" Econ Journal Watch 6.2 (2009): 218–238.

Editions
There have been three editions of More Guns, Less Crime: Understanding Crime and Gun Control Laws, all published by University of Chicago Press:
 * First edition, 1998, ISBN 978-0-226-49363-3
 * Second edition, 2000, ISBN 978-0-226-49364-0
 * Third edition, 2010, ISBN 978-0-226-49366-4