In light of the tragic mass shootings in Wisconsin and Colorado this summer, questions naturally arise about who has access to guns. But data about gun sales and research about the best public policies on weapons are scarce. There's a reason for that: money.
David Hemenway, professor of health policy at Harvard University and director of the Harvard Injury Control Research Center, said unlike research about motor vehicle safety and laws, there is "little" money for research involving guns.
Hemenway suspects that guns are a "hot button issue" and only a few foundations provide funding for research on guns and gun policies.
"We don't have good research or sensible policies. If we had this, we could say, 'These policies work well.' But we hardly know anything," Hemenway said.
Hemenway said high-profile incidents like the Oak Creek, Wis. temple shooting on Sunday morning are just the "tip of the iceberg."
"Lots of people are dying needlessly from suicide, homicide, and accidents," he said.
On Sunday, police shot and killed the gunman, identified as Wade Michael Page, who served in the Army from 1992 to 1998. The reported semi-automatic handgun used to kill six people was reportedly purchased legally from a licensed gun dealer.
The data that exists may be informative, but the picture is still incomplete about how many guns are sold, who has them and where they are coming from, public policy experts say. Individual gun companies don't as a rule release sales numbers.
On Friday, the FBI's National Instant Criminal Background Check System reported 1,300,704 background checks took place in July across the country. That's down from 1,302,660 background checks in June and up from 1,157,041 background checks in July 2011.
After the shooting in Aurora, Colo. last month, background checks for gun purchases spiked in the state, the Denver Post first reported. On July 20, the day after the midnight shooting, there were 1,216 approvals through InstaCheck, according to the Colorado Bureau of Investigation. The average for Fridays in July 2012 was 972 while the average for Fridays in July 2011 was 710. On Saturday, July 21, there were 1,243 approvals through InstaCheck while the average Saturday in July was 1,007 approvals. There were 705 approvals for Saturdays in July 2011.
Gun-control and public policy experts point out that background checks are not an exact indicator of gun sales for several reasons.
"The FBI background check data is a poor surrogate for actual sales data and the FBI itself warns not to use the data as an indicator of gun sales," said Josh Horwitz, executive director of the Coalition to Stop Gun Violence. "The most accurate indication of new gun sales would be the data from the industry itself, which they refuse to provide."
The National Sports Shooting Foundation, a firearms industry trade association, did not return multiple requests for comment. The National Rifle Association did not immediately return a request for comment.
"Companies as diverse as cell phone manufacturers and recreational vehicle manufactures routinely report the number of new units produced and sold," Howitz said. "The firearm industry has their own sales data but they prefer to use an imperfect marker instead."
Horwitz said it is not unusual for a person to go through the background check system more than once for the same purchase, for example.
A small percentage of people are denied guns while others don't follow through with the gun purchase despite having a background check, said Tom Smith, director of the General Social Survey at the University of Chicago's National Opinion Research Center (NORC), a social science research group established in 1941. Also, background checks only include purchases through licensed dealers. Some can legally purchase guns in private sales without checks. Illegally purchased or transferred guns are, of course, another problem.
Smith said it could be difficult for the firearms industry to aggregate their sales or ownership data, and not just for competitive reasons. Among the other possibilities are there are increasing numbers of small manufacturers and imports of guns into the U.S.
"I'm not sure if people in the industry even know what the total numbers are with each company keeping its own private records," Smith said.
One piece of information researchers found is that the percentage of households with a gun has declined from 1973 to 2011, according to Smith.
In 2010, about 32.3 percent of American households reported having any guns in the home, after hitting a peak in 1977, when 54 percent of households reported having any guns.
As Smith points out, however, "If a household has 20 handguns or one, it's still one household."
Josh Sugarmann, executive director of the Violence Policy Center, said that even if gun ownership is declining, the gun industry's "bright spots" in sales are assault weapons and what the gun industry calls self-protection handguns marketed as able to be concealed.
"Grandfather's rifle or the traditional market is fading," Sugarmann said.
Sugarmann said it is possible that the number of guns per owner in the U.S. is increasing.
"Certain guns develop a cache and they are sold for different reasons," he said.
A key element of the gun industry's sales strategy is to market assault rifles to law enforcement and the army, "which is legitimate use, and then they use a halo effect for creditability to market to the civilian marketplace," Sugarmann said.
The common thread in mass shootings in the U.S. is "very few pistols sold today have magazines with less than 10 rounds," he said.