State waiting periods for handgun purchases prevent about 750 gun deaths each year in the United States, new research has found.
An estimated 910 gun deaths could also be avoided if those policies were adopted nationwide, according to the study, published Monday in the Proceedings of the National Academy of Sciences.
“What we found is a law that doesn’t take guns away from anybody, doesn’t restrict anybody’s right to own a gun, and yet can significantly reduce gun homicides,” said Deepak Malhotra, an author of the study and a professor at Harvard Business School. Mr. Malhotra collaborated with Michael Luca, a fellow professor at the business school, and Christopher Poliquin, a doctoral student there.
The American Medical Association supports the adoption of such policies in fighting what it describes as the “public health crisis” of gun violence, and polls have shown broad public support for waiting periods. Last week, Quinnipiac University found that 79 percent of voters supported a mandatory waiting period for all gun purchases.
That the Monday study focused on a policy with such widespread backing was no coincidence: Mr. Malhotra and Mr. Luca said they were motivated to research politically viable gun control policies after the mass shooting at an elementary school in Newtown, Conn., in 2012.
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More than 33,000 people die from guns each year, most of them from suicides.
To investigate the effects of waiting periods, the team conducted two analyses.
The first, relying on data from 1970 to 2014, compared changes in the number of gun homicides in states that adopted waiting periods with such changes elsewhere, accounting for critical factors associated with gun violence, like alcohol consumption and poverty rates.
That analysis found that waiting periods were associated with a 17 percent drop in gun violence, or about three dozen fewer homicides per year in a state with an average number of gun deaths.
The second analysis relied on a natural experiment: the adoption of a national waiting period from 1994 to 1998 under the Brady Handgun Violence Prevention Act, named for the former White House press secretary James S. Brady, who was shot during an assassination attempt against President Ronald Reagan and was left permanently disabled. (In 1991, Mr. Reagan, arguing in favor of the measure, said waiting periods “would certainly” lead to fewer handgun deaths.)
Again, the authors found that waiting periods were associated with a 17 percent drop in gun homicides.
“What we can show with great precision, with a lot of robustness, is that if a state passes a waiting period law that delays the acquisition of a firearm by a few days, gun homicides go down,” Mr. Malhotra said.
The national waiting period requirement, an interim measure, was lifted in 1998 when the federal government introduced its national criminal background check system.
The study on Monday also found no link between waiting periods and homicides that did not involve a gun, suggesting that people who might have used the weapons to cause harm did not simply pursue an alternative means to commit the crime.
State waiting periods vary widely in length. In Illinois, some guns are subject to only a one-day wait, according to the Law Center to Prevent Gun Violence. In Hawaii, it takes two weeks to obtain the permit necessary to buy a firearm.
Waiting periods also appeared to reduce suicides, though that finding was not as consistent or robust as the finding on homicides, the authors said.