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In states with a mandated waiting period between a gun’s purchase and delivery, there are 17% fewer gun homicides.


Gun waiting periods could save hundreds of lives a year, study says

Good luck finding a legislative issue more controversial than gun violence—at least in the United States. Compounding the controversy is a dearth of reliable data, thanks largely to a de facto ban on federally funded firearms research enacted in 1996. Yet a new study funded by Harvard Business School suggests that one policy—a mandatory waiting period between the sale of a gun and its delivery—could save hundreds of U.S. lives each year if implemented nationally.

“Absolutely, this study demonstrates a robust association between waiting periods and gun deaths,” says Margaret Formica, a public health researcher at the State University of New York Upstate Medical University in Syracuse who studies firearms deaths but wasn’t involved in the new work. “It’s an innovative way of looking at this issue.”

More than 33,000 Americans die each year in gun-related incidents, including accidents, homicides, and suicides, about as many as in vehicle accidents. But regulations that place limits on the sale and ownership of firearms vary widely from state to state, and it’s unclear which measures might actually prevent gun violence. Some research from other countries has suggested that a “cooling off” period between the sale and delivery of a gun can tamp down suicidal impulses and anger-driven violence.

So when Harvard University researchers were motivated to contribute to policy-relevant gun research in the wake of the 2012 Sandy Hook Elementary School shooting, such “waiting periods” were an easy jumping-off point. Not only was there past research, but data on waiting-period laws are relatively easy to track down. “Instead of saying, ‘Isn’t it a tragedy, children are dying, oh well, on to the next meeting,’ we decided we wanted to do something,” says Deepak Malhotra, a negotiation and conflict resolution researcher who co-authored the new study with economist Michael Luca.

Along with doctoral student Christopher Poliquin, the pair examined the relationship between shooting-related homicides and suicides and state laws that delay the delivery of a purchased handgun by 2–7 days. Between 1970 and 2014, 43 states and Washington, D.C., had waiting period laws in place for at least 1 year. The researchers compared guns per capita homicide rates in states with and without the laws over the same time periods. They found that states with mandatory waits—no matter the total length—had on average 17% fewer murders and about 10% fewer suicides.

Although that’s an interesting correlation, Malhotra notes, it’s not enough to say that waiting periods themselves led to fewer deaths. So the researchers turned to a natural experiment. In 1994, the Brady Handgun Violence Prevention Act mandated background checks for all handgun purchases from licensed firearms dealers nationwide, as well as a 5-day waiting period to carry out these checks. That meant that 19 states without waiting periods suddenly had them. When the researchers analyzed the data, they found a sharp 17% drop-off in gun homicides and a 6% reduction in suicides when those states had waiting-period laws, they report today in the Proceedings of the National Academy of Sciences.

After 1998, instant computerized background checks did away with the mandatory waiting period, though some states kept their own laws on the books. In the 17 states with waiting period laws today, the researchers estimate that roughly 750 gun homicides are avoided each year. If all 50 states and Washington, D.C., had mandatory waiting periods, Malhotra says, an additional 910 lives would be saved annually.

Formica says that though the study does a good job of describing the relationship between waiting periods and gun deaths, it does have one major limitation: Because the researchers looked at population-level data and not at outcomes for individual gun purchasers, it’s a bit of a stretch to say with certainty that these waiting periods actively prevented deaths. “You can’t tell if gun purchasers were the ones directly affected, so you can’t know for sure that it’s a causal relationship,” she says.

Earlier this year, the researchers presented their findings to Representative Raja Krishnamoorthi (D–IL). Last week, he sponsored a bill that would enact a national 3-day waiting period between a gun’s purchase and its delivery, “about as long as you’d wait for an Amazon purchase,” Malhotra says. Given political opposition, Malhotra and Luca aren’t hopeful for the bill’s chances. But by presenting concrete, evidence-based data, they hope their study helps pave the way for politically viable legislation.

Because the federal spending bill that funds the U.S. Centers for Disease Control and Prevention has an amendment that prevents federal research dollars from being spent on studying gun violence, Malhotra and his team received funding from Harvard Business School. (AAAS, which publishes Science, has called on Congress to remove restrictions on funding firearms research.)

Last year, epidemiologist Sandro Galea from Boston University wrote in the American Journal of Public Health that social scientists should take up gun violence as a public health issue and seek alternative funding for gun policy studies. “This is exactly the kind of work that should be funded more,” he says of the current study. “Absent data, we cannot have a data-driven conversation about gun violence.”