Specifically:

Americans own an estimated 265m guns, more than one gun for every American adult, according to the most definitive portrait of US gun ownership in two decades. But the new survey estimates that 133m of these guns are concentrated in the hands of just 3% of American adults – a group of super-owners who have amassed an average of 17 guns each.

The unpublished Harvard/Northeastern survey result summary, obtained exclusively by the Guardian and the Trace, estimates that America’s gun stock has increased by 70m guns since 1994. At the same time, the percentage of Americans who own guns decreased slightly from 25% to 22%.

Also:

While there are an estimated 55 million American gun owners, most own an average of just three firearms, and nearly half own just one or two, according to the survey results.

Then there are America’s gun super-owners – an estimated 7.7 million Americans who own between eight and 140 guns.

This kind of concentrated ownership isn’t unique to guns, firearms researchers noted. Marketing experts suggest that the most devoted 20% consumers will typically account for 80% of a product’s sales.

And:

The number of women who enroll each year in the NRA’s basic pistol course almost doubled from 2011 to 2014, from about 25,000 a year to nearly 46,000 a year, according to NRA spokeswoman Catherine Mortensen.

Why super owners own so many guns:

The demographics of America’s 7.7 million gun super-owners were less diverse than gun owners overall, with super-owners more likely to be male, less likely to be black or Hispanic, and more likely to own a gun for protection, researchers said. This subset of gun enthusiasts – only 14% of all gun owners – has amassed a collective 133m firearms.

Interviews with Americans who own at least 17 firearms revealed a wide range of reasons for accumulating so many guns.

Some super-owners are dedicated collectors with special rooms to display their assortment of historic firearms. Others are firearms instructors, gunsmiths, or competitive shooters, who need a variety of firearms in the course of work or competition. Some gun owners have a survivalist streak, and believe in storing up weapons, as well as food and water, in case of a disaster scenario. Others simply picked up a handgun here, a shotgun or hunting rifle there, and somehow ended up with dozens.

“Why do you need more than one pair of shoes?” said Philip van Cleave, the president of the Virginia Citizens Defense League, a gun rights group that views itself as being to the political right of the NRA. “The truth is, you don’t, but do you want more than one pair of shoes? If you going hiking, you don’t want to use that one pair of high heels.”

“Walking around the beach with shirt off and shorts … I’m probably going to use a different gun than putting on a sport coat and going out to dinner,” he said.

How many guns are in America?

The new survey results mirror the trends of the annual General Social Survey, which found that household gun ownership has fallen from 50% to close to 31% since the late 1970s, and that individual gun ownership fell from 28% in 1980 to 22% in 2014. 

But as with most aspects of American gun politics, the basic data on American gun ownership is hotly debated, with some gun rights supporters arguing that American gun ownership is not on the decline, and that Americans may be under-reporting their gun ownership in some surveys.

A Gallup poll last year estimated personal gun ownership at 28%, while a Pew Research Center survey put it at 31%, which would make the estimated total of American gun owners more than 75 million, compared with 55 million in the Harvard/Northeastern study.

The Bureau of Alcohol, Tobacco and Firearms tracks the numbers of firearms manufactured in or imported into the United States, as well as how many background checks on gun sales licensed firearm dealers process. 

Manufacturing and import records suggest that more than 360m firearms entered the US market between 1899 and 2013, the new study’s authors noted. With gun sales spiking since 2013, some estimates would put the total number of American firearms today around 400m. 

However, it’s not clear how many American guns have been broken, confiscated and destroyed by the police, smuggled out of the country, or otherwise left the gun stock over the decades.