By CALVIN WOODWARD, Associated Press

WASHINGTON (AP) — Some of the numbers being hurled around in the gun control debate passed their freshness date eons ago. Perhaps none is more prominent than the claim that 40 percent of gun sales take place without background checks.

The statistic is ubiquitous these days and cited as gospel by a variety of public figures and gun-control advocates, President Barack Obama among them, but it is 20 years old and was not much more than an educated guess at the time.

It's no wonder policymakers are grasping at tatters of moldy data as they consider expanding background checks and banning certain weapons and ammunition. A 1996 law pushed by the gun-rights lobby closed the spigot on federal gun research, leaving scholars, private groups and states to pick up some pieces. Only now, under a recent order by Obama, can federally financed research resume.

No one questions that criminals get their hands on guns, and do so primarily from the off-the-books market. But no one knows how many guns skirt the criminal-check system by taking place at gun shows, in private transactions or otherwise outside the regulated channels. Public policy research is scarce on the subject.

Into this statistical vacuum rush voices of certitude.

OBAMA, on Jan. 16: "It's time for Congress to require a universal background check for anyone trying to buy a gun. The law already requires licensed gun dealers to run background checks, and over the last 14 years that's kept 1.5 million of the wrong people from getting their hands on a gun. But it's hard to enforce that law when as many as 40 percent of all gun purchases are conducted without a background check. That's not safe. That's not smart. It's not fair to responsible gun buyers or sellers."

MAYORS AGAINST ILLEGAL GUNS, a coalition favoring tighter gun controls, on Tuesday: "Around 40 percent of U.S. gun transfers are conducted by unlicensed 'private sellers' who are not required to conduct a federal check, and who often do business at gun shows and on the Internet."

NEW YORK MAYOR MICHAEL BLOOMBERG, Dec. 17: "Congress should pass the Fix Gun Checks Act, which would close the 'private sale loophole' that allows more than 40 percent of gun sales to go through without a background check."

REP. DAVID CICILLINE, D-R.I., Jan. 26: "More than 40 percent of sales nationally are made without background checks."

VICE PRESIDENT JOE BIDEN, Jan. 17: "Because of the lack of the ability of federal agencies to be able to even keep records, we can't say with absolute certainty what I'm about to say is correct. But the consensus is about 40 percent of the people who buy guns today do so outside the ... background check system."

THE FACTS:

Biden stands alone here in acknowledging he may be saying something that isn't right.

The claims that gun sales made without background checks comprise "more than," ''as many as," ''nearly" or "about" 40 percent of all gun sales are rooted in a poll looking broadly at gun ownership in America. Sponsored by the Justice Department through a grant to the Police Foundation, the poll's principal relevance today is as a snapshot of the way things were when it was taken — 1994.

The research reported on the nature of gun acquisitions made in 1993 and 1994, asking people who had obtained guns then where the guns had come from and whether they thought the source was a federally licensed dealer. Transactions through licensed dealers were considered covered by the background check system, which was just then coming into effect.

Although the survey interviewed more than 2,500 Americans, just 251 had acquired guns during that time frame, a small sampling from which to make a general conclusion.

In all, 64 percent of those respondents reported acquiring a gun from a source they thought to be a licensed dealer, suggesting that 36 percent of gun acquisitions were in the secondary and unregulated market.

But the study's researchers found considerable ambiguity and some apparent contradictions in the responses. With a clear picture eluding them, they estimated 30 percent to 40 percent of the acquisitions were off the books and would not have been subjected to a background check.

Only 4 percent of gun sales were thought to have come through gun shows or flea markets — a corner of the market that is a top concern today for those who want to expand background checks to close the "gun-show loophole," as Obama's proposals would do.

More than 17 percent of guns acquired in 1993 and 1994 came from a family member, according to the poll — a source of weapons that would remain largely unregulated in pending Senate legislation calling for expanded checks.

Discounting family acquisitions, the percentage of gun transactions eluding background checks — whatever that figure is — would be considerably less.

The statement by the coalition of mayors followed a Senate Judiciary Committee vote along partisan lines Tuesday to expand background checks. The bill's prospects are uncertain.

In contending that 40 percent of gun transfers are conducted by private sellers, often "at gun shows and on the Internet," the mayors stretched a thin claim even thinner.

They cited the same old study as everyone else — one that was done well before the spread of online commerce. The study considered purchases by mail order — 3 percent of reported gun acquisitions — but makes no mention of online transactions.

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AP Polling Director Jennifer Agiesta and AP writer Alan Fram contributed to this report.

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Online:

Police Foundation Guns in America survey: http://www.policefoundation.org/content/guns-america

EDITOR'S NOTE _ An occasional look at political claims that take shortcuts with the facts or don't tell the full story