Research News

Do Gun Laws Lead to More, or Less, Crime?

Charles Manski explains why study results often conflict


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Do right to carry laws lead to more, or less crime? Can we even tell?

Does allowing citizens to carry guns deter crime, or lead to more of it?

“On the one side, there are people who say that if honest citizens are carrying guns, they will deter criminals from acting,” said IPR economist Charles F. Manski. On the other side, he added, there are those who say that more guns lead to increased crime instead. To complicate this debate further, studies of gun laws have reached vastly different conclusions as to their effects.

In a new IPR working paper, Manski and his colleague, the University of Virginia’s John Pepper, seek to explain, as Manski put it, why it is “that people who use the same data can wind up with such different conclusions.”

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Charles Manski

The researchers look at the impact of laws allowing individuals to carry concealed handguns—known as “right-to-carry,” or RTC laws—on annual crime rates in Virginia, Maryland, and Illinois from 1970–2007, using data from the Federal Bureau of Investigation’s Uniform Crime Reports. 

Their results are “nuanced,” Manski said: “It depends on the time period and it depends on what crime you are talking about.”

Other researchers came to such different conclusions, he explained, because “the conclusions you draw depend on what kinds of theories or assumptions you combine with the data.” Manski and Pepper advocate assumptions that take into account the possibility that the effects of RTC laws might vary across years, states, and crimes. Previous researchers’ assumptions have been less flexible.

Why the need for flexibility? Take Manski and Pepper’s finding that gun laws appeared to decrease some crime rates in the 1990s yet increase them in the 2000s. “There’s nothing mysterious about that, actually,” Manski said, because high crime rates in the 1990s may have given more scope for a deterrent effect while lower crime rates in the 2000s may have done the opposite. So if other researchers failed to take this into account in their estimates, they might depict a very different story.

While more flexible assumptions might not lead to the conclusions policymakers crave—absolute statements like “more guns, less crime”—these assumptions are more realistic when it comes to uncertainty and possibility.

“There is no single answer that right to carry laws are always good or always bad,” Manski concluded. “Policymaking is going to have to face up to the uncertainty.”

Charles F. Manski is Board of Trustees Professor in Economics and an IPR fellow.

Photo credit: Scott Beale/laughingsquid.com