Rick Jervis

USA TODAY

Despite steep declines in violent crimes, an estimated 70 million firearms were added to American arsenals the past two decades, according to a new landmark study on gun ownership.

Overall, Americans own an estimated 265 million guns – more than one gun for every American adult, according to the study by researchers at Harvard and Northeastern universities. Half of those guns – 133 million – were in the hands of just 3% of American adults, so-called “super owners” who possessed an average of 17 guns each, it showed.

The survey, the most authoritative since a 1994 study posed similar questions to gun owners, is under peer-review for publication in a trade journal. Summaries of the study were released this week to the Guardian and The Trace news outlets.

The findings include:

An estimated 55 million Americans own guns.

The percentage of the U.S. population who own guns decreased slightly from 25% in 1994 to 22% last year.

Between 300,000 and 600,000 guns are stolen each year.

Gun owners tend to be white, male, conservative, and live in rural areas.

25% of gun owners in America are white or multi-racial, compared with 16% of Hispanics and 14% of African Americans.

There are an estimated 111 million handguns nationwide, a 71% increase from the 65 million handguns in 1994.

Researchers found that the top reason people owned guns was for protection from other people, even though the rate of violent crime has dropped significantly the past two decades, said Deborah Azrael, director of research at the Harvard Injury Control Research Center and one of the study's authors.

Azrael said the study tried to update numbers and trends that hadn’t been reviewed in two decades. Separate reports on background checks and gun storage, based on the same survey, are scheduled to be released later this year.

“In a country where 35,000 people a year die by firearms, we haven’t been able to come out with a survey on gun violence for 20 years,” she said. “That’s a real failure of public health and public policy.”

Over the years, Congress has pulled funding from agencies like the Centers for Disease Control and Prevention to deter in-depth reviews of gun violence, said Daniel Webster, a gun violence researcher at Johns Hopkins University.

The Harvard/Northeastern study is important because it examines the number of guns found in respondents' home and their motivation for owning them, he said. “People’s perception of risk and need to have a gun does not correlate with their actual risk,” Webster said. “That’s the most important thing for us to understand.”

The super owners consisted of an estimated 7.7 million Americans and owned between eight and 140 guns each. Nearly half of gun owners owned just one or two guns. Those owners merit further study to try to bring down the nation’s suicide rate, Azrael said

More than half of all suicides in the USA – or about 21,000 a year – are committed with a firearm, according to the CDC.

Philip Cook, a Duke University researcher and co-author of the landmark 1994 study, said Azrael's study is important in further understanding gun deaths and the forces behind them. "The very idea that something as fundamental as many how many Americans own guns is only measured once every 20 years seems surprising," he said. "But that's the world we live in."

Azrael said she was able to tap into funding from the Fund for a Safer Future, a consortium of donors created after the 2011 shooting of Congresswoman Gabrielle Giffords and 18 others near Tucson, Ariz. That fund was further bolstered in the wake of the Sandy Hook Elementary shooting, where a gunman shot and killed 20 elementary-aged students and seven adults before shooting himself, she said.

The study was based on an online survey of nearly 4,000 Americans conducted in 2015 by market research company GfK, with a nationally representative panel of opt-in participants who are paid to complete surveys, she said.