A new study finds that requiring a waiting period reduces firearm homicides by 17 percent.
According to the study, at that rate, the country could save 910 lives a year by ensuring every state has a waiting-period law—a mandated interval between when people buy guns and when they're actually able to take them home. Sixteen states and the District of Columbia currently have such laws, which mandate waits of anywhere from three to 14 days. The existing laws prevent about 750 homicides a year, the study finds.
"What we show, pretty definitively, is that a waiting-period law can significantly reduce the number of gun homicides," says Deepak Malhotra, one of three Harvard Business School professors who worked on the study, which appeared in the Proceedings of the National Academy of Sciences. "It does seem to create a cooling-off period that leads to this reduction."
Outside experts say Malhotra and his team's work strengthens the evidence that waiting periods save lives. Crime researcher Phil Cook rated the science behind waiting periods as now being at "a B or B-plus"; epidemiologist Cassandra Crifasi says, "With this study, we are approaching pretty darn convincing."
Malhotra and his team looked at the homicide and suicide rates in states that passed and repealed waiting-period laws any time between 1970 and 2014. They also analyzed the effect of the Brady Handgun Violence Prevention Act, the nation's biggest federal gun act, which temporarily created waiting periods for handgun buyers between 1994 and 1998. In both data sets, they found that waiting-period laws led to fewer homicides by firearms. They also found the laws prevented suicides, but the reduction wasn't as big and the association wasn't as strong. Both shorter (two to three days) and longer (four to seven days) pauses helped about the same.
Researchers often can't say a policy caused certain outcomes. Rather, they usually say a law is associated with certain results. But in this case, both the Harvard researchers and outside experts say this study truly shows cause because of how long of a period it analyzed and because of the careful way it was designed, which tried to isolate the effect of waiting from other factors that might cause homicides to fall, such as states' demographics or economies.
It's not known exactly why waiting periods work. Most researchers think that they deter people who, in a moment of intense anger or sadness, decide they'll buy a gun and commit violence. The extra days might give such folks time to rethink their feelings. But it's also possible that other factors are at play. Maybe the wait lets the opportunity for some crimes to pass, for example.
Either way, Malhotra and his colleagues are hoping their work means waiting-period laws will spread. "We can reduce gun deaths without taking guns away from anybody," he says. "Every state could do this on their own."