Are firearm sales on the rise? Probably, but gun control advocates say data is murky

— -- As the debate over gun laws rages anew in the wake of last Friday's horrific shooting in Aurora, Co., advocates for stricter legislation say there's one major question mark in the debate: No one knows exactly how many firearms are sold in America.

While the ATF compiles detailed statistics on gun sales, the information is delayed by over a year to comply with federal trade secrets law. For more current information, both firearm trade groups and advocacy organizations typically rely on the number of background checks that the FBI runs on prospective buyers each month, even as they agree this measure is imprecise. These checks are conducted on purchasers buying from federally licensed vendors, but do not fully capture private sales—the so-called " gun show loophole."

The number of background checks related to handguns, rifles, shotguns and other "long guns" has risen steadily in the past two years, a fact that trade groups like the National Shooting Sports Foundation  readily advertise. There was a modest spike in checks after Sept. 11, 2001, and a much larger one after Barack Obama won the 2008 election. (Since gun sales are highly seasonal, the data is best viewed as a percent change over the same month in the previous year. The data below does not include background checks relating to permits.)

Few people dispute that the growth in background checks means people are buying more guns. But Josh Horwitz, the executive director of the Coalition to Stop Gun Violence, warns against connecting background check figures too directly with purchases. "That data was never meant to be sales data," he says. "One person purchasing a firearm can have his name run through the [National Instant Criminal Background Check System] two or three times."

The National Rifle Association referred calls about gun sales data to the NSSF, which did not return repeated requests for comment. The NSSF has suggested the more recent upward trend is related to fears that Obama will focus on gun control laws if he wins reelection,  Politico reported last week.

In general, gun trade groups have also pointed to profits from publically held gun manufacturers or ATF data on firearm sales, which is reported with a two-year delay. NSSF press releases on gun data state that the background check data is "not a direct correlation to firearms sales."