How freely do guns flow in the United States compared with the world's other industrialized countries?
According to GunPolicy.org, run by Philip Alpers, a firearms analyst at The University of Sydney, the United States is unusual with what Alpers described as the "two pillars" of gun control: licensing gun owners and registering weapons.
"You are basically the only country in the developed world that doesn't license gun owners across the board and you are almost alone in not registering guns across the board," Alpers said. "It's very difficult to compare [the U.S.] with others, because you simply don't have those things." New Zealand and Canada are the other developed countries that don't register guns across the board, Alpers said. The two countries register handguns and military-style semi-automatics, but not rifles and shotguns.
The Small Arms Survey, an independent research project based in Geneva, noted that of the 28 countries it surveyed for its 2011 report on civilian firearm possession, only two consider civilian ownership of a firearm a basic right: the U.S. and Yemen. But even Yemen has begun clamping down on civilian guns, Alpers said.
In the U.S., some often equate gun registration as government overreach. Joseph Olson, a law professor at Hamline University in Minnesota, said he is a proponent of this view. Governments can use "registration and licensing lists to go out and make sure there cannot be any resistance" Olson told The Huffington Post. He said the other problem with registration is that it focuses on "law-abiding people who aren't a problem."
In addition to lax gun regulation, the U.S. stands out in the sheer number of guns. According to the Small Arms Survey, the estimated total number of guns held by U.S. civilians is 270 million -- 88.9 firearms per 100 people. The country with the second-most guns is India, with an estimated 46 million guns in private hands -- or about four firearms for every 100 people.
The U.S., with 4.5 percent of the world population, accounts for about 40 percent of the planet's civilian firearms, said Dr. Garen Wintemute, of the University of California, Davis, Medical Center.
The U.S. is not a uniquely violent society, said Wintemute, who practices emergency medicine and conducts research on the nature and prevention of gun violence. Our overall rates of violence are similar to Australia, Canada and Western Europe. Where the U.S. stands out, Wintemute said, is in the homicide rate.
"That's a weapon effect. It's not clear that guns cause violence, but it's absolutely clear that they change the outcome," said Wintemute.
Other countries have homicide rates comparable with the U.S. or worse, Alpers said. But they're not exactly models of public safety. United Nations Office on Drugs and Crime data shows 10,300 homicides by firearms in the U.S. 2009, compared with 8,804 in Mexico and 12,808 in Colombia.
Adjusting for population, the U.S. death rate by firearms -- which includes homicides, suicide and accidents -- was 10.2 per 100,000 people in 2009, according to theCoalition for Gun Control. The closest developed country was Finland, with a firearms death rate of 4.47 per 100,000 people in 2008, less than half that of the U.S. rate. In Canada, the rate was 2.5 per 100,000 people in 2009. In the United Kingdom, the 2011 rate was 0.25 per 100,000 people.
Olson argued that while everyone talks about gun violence, violence itself is the problem.
"People have been killing each other since Cain and Abel and they will continue to do so," Olson said. "Really bad guys who are willing to kill have no problem getting guns." Olson conceded, however, that gun-purchasing restrictions could be tougher, especially for violent offenders.
With the Connecticut school massacre and the revival of the U.S. gun control debate, Wintemute said the national conversation has mainly been "dominated by voices at the extremes" and that the rest of the country falls somewhere in the middle. The general population -- including gun owners -- overwhelmingly support stricter background check measures, according to a poll conducted for the coalition Mayors Against Illegal Guns.
Wintemute said that expanding reasons to deny gun purchases, including a history of misdemeanor violence and alcohol abuse, may meaningfully reduce gun violence within a year or two.
"I think that it would be wonderful if we rethought our relationship with guns and took on some of the deep social thinking that people have talked about," Wintemute said. "But in the meantime, let's do some things that work."