An estimated 6 million American adults carried a loaded handgun with them daily in 2019, double the number who said they carried a gun every day in 2015, according to a new study published in the American Journal of Public Health.

The new estimates highlight a decades-long shift in American gun ownership, with increasing percentages of gun owners saying they own firearms for self-defense, not hunting or recreation, and choosing to carry a gun with them when they go out in public, said ​​Ali Rowhani-Rahbar, a professor of epidemiology at the University of Washington, and the study’s lead author.

A landmark supreme court case this summer overturned a New York law that placed strict limits on public gun-carrying, ruling, for the first time, that Americans have a constitutional right to carry a handgun for self-defense outside the home.

While recent surveys show that nearly a third of American adults say they personally own a gun, the percentage who choose to regularly carry a firearm in public is smaller, with about a third of handgun owners, or an estimated 16 million adults, saying they carried a loaded handgun in public at least once a month, and an estimated 6 million saying they did so daily, the study found.

But public gun-carrying has appeared to increase rapidly in recent years. A 2015 study by the same researchers, using the same methodology, had found that 3 million adults said they carried a loaded handgun daily, and 9 million did so once a month.

Today, the number of adults carrying a gun daily is probably even higher than the 2019 estimate, thanks to a record-breaking increase in gun sales during the pandemic, Rowhani-Rahbar said. “We have every reason to believe this is a trend that is probably going to continue,” he added.

The 2019 study is the most recent available peer-reviewed estimate of how many Americans regularly carry guns in public, he said, and an equivalent post-pandemic survey has yet to be conducted.

While the effect of permissive gun-carrying laws on gun crime has been sharply debated inside and outside research circles, “the totality of evidence is leaning toward an association between those [permissive] policies and an increase in violence,” Rowhani-Rahbar said.

But he said more research is needed, including increased examination of how often “carrying results in self-defense or protection in a way that saves lives”, as many American gun owners believe it does.

Demographically, those who chose to carry a gun in public in 2019 were more likely to live in the south, the study found. Four in five gun carriers were male, and three in four were white, Rowhani-Rahbar said. Other demographic factors, like education and household income, did not make a difference in whether gun owners chose to carry their guns in public or not, he said. About a quarter of the gun carriers had a household income of at least $125,000 a year, and nearly a third had graduated from college, the researchers found.

Only about 8% of handgun owners and carriers were at the lowest income level, making less than $25,000 a year.

The increase in self-reported handgun carrying comes as more US states have passed laws to make it easier to carry a gun in public, with dozens of states removing the requirement that residents had to obtain a “concealed carry permit” in order to carry a concealed firearm on their person.

“The country has been moving as a whole, in the past two or three decades, very clearly and dramatically toward loosening gun-carrying laws,” Rowhani-Rahbar said.

Rowhani-Rahbar’s study found that a lower percentage of gun owners chose to carry in public in states that had very strict carrying laws, but that there wasn’t a substantial difference between states where it was easy to get a permit and states that required no permit at all.

But the handful of large states that had strict carrying laws, including New Jersey and California, are now in the process of changing them, thanks to the supreme court’s decision in New York State Rifle & Pistol Association v Bruen this June, said Adam Skaggs, the policy director at the Giffords Law Center to Prevent Gun Violence, which advocates for increased regulation of firearms.

“Bruen is only going to accelerate the number of people carrying guns in public,” Skaggs said, noting that, anecdotally, the number of gun-carrying permits being issued in those states is already on the rise.

The 2019 gun-carrying study was based on the self-reported behavior of a nationally representative sample of US adults living in firearm-owning households. Because of opposition from gun rights advocates, there are no official government statistics on the number or demographics of US gun owners, or even the exact number of annual consumer gun sales in the US, meaning that survey-based estimates are sometimes the best statistics available.