Lawmakers in statehouses and the U.S. Capitol who are debating proposed new firearm laws are lacking some key data: How many people in the U.S. own guns, and how many households contain guns?
Some surveys suggest only 50 million Americans own guns. Others, depending on how they are interpreted, point to a number closer to 90 million. The National Rifle Association puts the total at 100 million. Household estimates are similarly varied.
Some researchers say gun owners may be less inclined to tell pollsters about their guns than they used to be. Here, guns displayed on a table at a gun show in Albany, N.Y., in January.
Some surveys show ownership rates declining, but whether that’s simply because Americans have become less likely to tell strangers they own guns is "an open question," said Arthur Kellermann, a policy analyst at the think tank RAND Corporation.
Referring to the General Social Survey’s finding last year that 34% of households have guns, down from percentages in the mid-40s in the early 1990s, Dr. Kellermann, an emergency physician, said, "Is it really 34%, or are there 10% of people out there who told the survey researcher ‘no’ but they have an assault rifle in the closet? That’s a question I can’t give you the answer to."
The director of the GSS, which is run out of NORC, an affiliate research institution at the University of Chicago, said he is confident most Americans answer the survey honestly. Tom W. Smith cites the structure of the survey, conducted in person over about an hour and a half. "It’s asked well into a survey," he said. "They’ve already told us all kinds of things about themselves." He said less than 1% of respondents have refused to answer the question in the history of the survey, which goes back 40 years, though refusal rates have gone up recently: to 3.6% in 2010 and 2% last year.
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Some researchers, however, say owners may be less inclined to tell pollsters about their guns than they used to be. They point to federal gun laws passed in the early 1990s and the stiffer gun restrictions proposed after December’s shooting in Newtown, Conn.—as well as messages from the NRA and other gun groups highlighting potential threats to ownership from the government. "It’s a different political era," said Dr. Kellermann.
Gary Kleck, a criminologist at Florida State University, points to Gallup surveys that find a much higher rate of ownership than does the GSS, with guns in 43% of American households and owned by 29% of American adults last year. He thinks these figures are more reliable because they are based on phone surveys, while the GSS is fielded in person. "People are more reluctant to admit to gun ownership or anything controversial or legally questionable in non-anonymous surveys," he said.
Other researchers say they prefer the GSS for its greater sample size and higher response rate. Each poll’s finding also is echoed by at least one other survey, clouding the picture. Pew Research has largely agreed with the GSS, while the ABC News/Washington Post poll has lined up with Gallup.
The NRA cites Gallup’s poll, not the GSS’s, as a source for its estimate of 100 million owners. Even Gallup’s numbers, though, suggest there are at most 90 million, and that assumes ownership rates from a poll of adults apply to the whole population. The GSS’s latest numbers suggest about 50 million adults, and less than 70 million people of all ages, own guns.
NRA spokesman Andrew Arulanandam said the group’s estimate was based on Gallup’s 2011 finding that 34% of American adults own guns. (That was the only Gallup poll since the firm started asking about ownership in 2000 that found a rate over 30%.) He added that other data—such as a record number of federal background checks for gun purchases in December—suggests ownership is increasing. "It’s fair to assume some are existing gun owners, but it’s also reasonable to assume some are new gun owners," he said.
Surveys also contribute to uncertainty in counts of guns themselves. These mostly center around 300 million for the U.S., based in part on a 2004 phone survey of 2,770 adults overseen by researchers at the Harvard School of Public Health. However, in reaching their estimate of 280 million guns, researchers calculated a figure of five guns per owner without using the totals from the 3% of owners who said they had 25 or more guns. Including them would have lifted the estimate to about 380 million. "You don’t want a couple of people who may not be reporting accurately to really skew the results," said study co-author David Hemenway.
Frank Newport, Gallup editor-in-chief, said it’s a mystery why surveys have diverged. "It’s an intriguing social-science puzzle as to why we are seeing the differences," he said. "I’ve learned in my career that the best answer to these kinds of questions is to get more data."
A version of this article appeared March 23, 2013, on page A2 in the U.S. edition of The Wall Street Journal, with the headline: Gun Counts Can Be Hit-or-Miss.