Nearly 40,000 people were killed by firearms in the United States in 2018, but curbing these numbers has been a stastically tricky—and politically fraught—problem. Now, a study that tracked individual gun laws over time suggests states can reduce gun deaths significantly by doing three things: limiting children’s access to guns, restricting concealed-carry permits, and restricting “stand your ground” policies.
The study isn’t without its flaws, but the basic findings make sense to Elinore Kaufman, a surgeon and public health policy analyst at the University of Pennsylvania. “Stand your ground laws encourage individuals to try to solve problems with bullets,” she says, as do right-to-carry laws. But laws that limit access to guns for children, she says, could help prevent firearm suicides by making it harder for everyone—not just children—to access guns in the first place.
U.S. gun laws vary considerably by state. Some, like Kansas, allow citizens to carry firearms in public and make it legal for gun owners to shoot an assailant in self-defense in some situations (known as the stand your ground doctrine). Others, like California, are more restrictive, limiting not only who is allowed to carry guns in public, but also access to firearms in the home by requiring safety devices such as trigger locks or gun safes.
This patchwork—combined with limited funding for reasearch—has made it hard for scientists to predict the effects of gun laws on gun deaths, says Terry Schell, a senior behavioral scientist at the nonprofit RAND Corporation, which aims to improve public policy through research and analysis.
To limit these problems, Schell and colleagues focused on just three kinds of laws and one outcome: gun deaths per capita. To understand how laws affect death rates, they screened hundreds of existing and novel statistical approaches, finally zeroing in on a model that reduces statistical noise by paying special attention to how different variables affect deaths year by year, rather than averaged over long periods of time.
The researchers counted the number of gun deaths from all 50 states for each year from 1980 to 2016. They then examined each instance of a new law limiting or allowing right to carry, stand your ground, or child access, state by state, through 2013. Finally, they compared that with mortality data from the Centers for Disease Control and Prevention (CDC) for the next 6 years.
On average, establishing right-to-carry and stand your ground laws resulted in a slight uptick in annual gun deaths—about 3% for each law, the team reports today in the Proceedings of the National Academy of Sciences. Conversely, creating laws aimed at making it harder to for children to get their hands on guns—say, by requiring parents to keep guns in safes—reduced gun deaths by an average of 6%. States that enacted strict child access laws, make it illegal to carry a gun in public without a permit, and don’t have a stand your ground law could expect to see an 11% reduction in annual gun deaths, according to the new model.
Eight states presently have that constellation of laws—California, Connecticut, Delaware, Hawaii, Maryland, Massachusetts, New Jersey, and Rhode Island—and six of those states are in the bottom 10 for per capita gun deaths, according to CDC’s state-by-state firearm mortality data.
However, because the study looked at a relatively small subset of gun laws, more research is needed to adequately understand how different laws such as background checks and waiting periods impact gun deaths, Kaufman says. And she suggests future studies could examine how these laws and their enforcement in different communities might also affect the impact that such laws have in different places.
Ali Rowhani-Rahbar, an epidemiologist at the University of Washington, Seattle, who studies gun policy, adds that it will also be important for such models to look at nonfatal gunshot injuries to better understand the impact of guns on communities and public health.
For now, Schell hopes providing more statistically valid data about the effects of different types of gun laws will help policymakers take action on this issue. Kaufman agrees. “Scientific evidence alone is not going to be enough to convince lawmakers who are opposed to any restriction on firearms,” she says, “but I still believe that building the evidence base can slowly change the minds [that are open to change].”