Americans are the proud owners of some 46 percent of the world’s civilian-owned firearms — both illegal and legal, according to a new decade-long study.

The research, from the Small Arms Survey, found that, globally, civilians are acquiring firearms at an increasing rate. But most of the total increase is attributable to gun-buyers in the U.S.

Of the approximately 1 billion firearms in the world, 857 million are in civilian hands, found the project, based at Graduate Institute of International and Development Studies in Geneva, Switzerland. Of those guns, about 393 million are owned by U.S. civilians. And between 2006 to 2017, U.S. gun owners acquired some 122 million guns. That accounts for more than half of the 207 million new firearms that civilians across the world picked up during that decade.

The survey’s authors acknowledge the difficulty of accounting for every gun in the world: Patchy gun registration systems are in place in many countries (including the U.S., which only requires federal registration of certain kinds of weapons). Of all the guns owned by civilians, the survey estimates that only 12 percent were registered with governments.

Survey author Aaron Karp, senior consultant at the Small Arms Survey, told VICE News that because of the difficulty of counting all the guns in the world, they relied on a variety of data sources. “The basic method is eclectic,” he said. “We take data where we can find it.”

The survey authors collected gun registration data where they had it, but not all countries have reliable data. In certain parts of the world, guns are also largely built from scrap parts, making them hard to count. And guns bought and sold on the black market are often missed in accounting or the total number of guns in any country.

When the authors couldn’t find registration data, they compiled their own and used estimates from law enforcement officials and academics only as a last resort.

Some of the increase in the global gun ownership figures had to do with with methodological improvements in their survey.

“We got a lot better at estimating,” Karp said. “Many more countries are reporting their civilian registration data,” he added.

But changes in their survey don’t account for the increase in gun ownership in the U.S. People in the U.S. are just buying a ton of guns — about 14 million per year, according to Karp.

According the survey, there were 120.5 guns in the U.S. for every 100 people. That’s more than a gun per person — and more than twice the rate of gun ownership in the country with the next most guns per capita, Yemen, where there's about one gun for every two people.

In places like Indonesia, Japan, and Malawi, by contrast, have some of the lowest rates of gun ownership. In those places, the researchers counted fewer than one firearm per 100 people.