Dave Kopel is research director at the Independence Institute, a free-market think tank in Colorado (http://i2i.org). His most recent book, with Paul Blackman, is No More Wacos: What’s Wrong with Federal Law Enforcement and How to Fix It.

Gun prohibition kills people. Guns in the hands of responsible citizens save lives and make everyone safer—even the employees of gun-control organizations. University of Chicago economist and law professor John R. Lott, Jr., proves those claims beyond a reasonable doubt in his new book, More Guns, Less Crime: Understanding Crime and Gun Control Laws. Single-handedly, Lott has redefined the gun-control debate in the United States.

Lott first appeared on the national firearms-policy scene in 1996 with the release of his research about concealed-carry laws. As of 1985, only a handful of states allowed citizens to legally carry firearms in the streets and other public places for protection. But now, 31 states do so; except for Vermont and Idaho (outside Boise), which require no permit at all, all of the states have some type of “shall issue” law. Under these laws, an ordinary citizen who passes a background check—and in some states, safety training—is issued a permit to carry a handgun for lawful protection.

Lott’s meticulous research far surpassed all previous work on the effects of those laws. He collected data from 3,054 counties in the United States over a 15-year period and examined changes in the rates for nine different crimes, not just homicide. He also accounted for the effects of dozens of other variables, including changes in arrest rates, changes in the age and racial composition of a county’s population, changes in national crime rates, and other changes in gun-control laws, including the adoption of waiting periods.

The results? Concealed-handgun license laws significantly reduce violent crime. The rates of homicide, rape, robbery, and aggravated assault fall between 5 and 8 percent. Crimes begin dropping immediately, but the full benefits of concealed-handgun laws take about three years to make themselves fully felt. The larger the percentage of the population with permits, the greater the drop in crime.

Lott also found a small but statistically significant increase in non-confrontational property crimes such as larceny. Apparently, concealed-handgun laws do not erase criminals’ appetite for other people’s property, but the laws do encourage the more rational criminals to acquire the property in ways that do not risk their lives.

More Guns, Less Crime includes additional research that Lott has conducted since 1996. For example, he found that after one state enacts a concealed-weapons law, crime rates in neighboring states without concealed-weapons laws tend to increase; criminals who live near state borders make sure to choose victims who can’t protect themselves.

The best antidote to guns in the wrong hands is guns in the right hands. Lott’s data show that states with concealed-handgun laws enjoy a 69 percent lower rate of mass murders in public places than states without such laws, all other things being equal.

Despite the high level of statistical sophistication in More Guns, Less Crime, the book is pleasant to read. Lott lays out the data in an accessible manner, building from simpler statistical models to more complex ones. The book serves not only as a guide to firearms policy, but as a readable introduction to multivariate statistical analysis.

The most interesting part of the book, however, is the chapter in which Lott addresses the criticism of his research. In marked contrast to the anti-gun researchers funded by federal Centers for Disease Control and Prevention, Lott has made his data readily available to any and all researchers.

To the anti-gun movement, the statistics on crime deterrence are irrelevant. But anyone with an interest in rational firearms policy ought to thank John Lott for writing this excellent book. More Guns, Less Crime would be a fine gift for your state representative, local newspaper editor, or public library.