Background checks for gun buyers are a hot political topic, and proponents of expanding them often cite a loophole at gun shows and online.
So how many guns are we talking about? No one really knows.
The Brady Campaign estimates 40 percent of all gun sales are completed without a background check, but that statistic is based on a survey released in 1997 and there's no way to know whether that percentage holds true today.
Background checks are required for all sales through federally licensed firearms dealers, regardless of whether the sale is in a store, at a gun show or online. But multiple laws prevent the government from keeping track of those sales in a centralized database.
The U.S. Department of Justice estimates there are somewhere between 2,000 and 5,200 gun shows in the U.S. each year. But no one really knows how many private sellers, the ones not required to run background checks, set up booths at those shows.
The latest study by the Bureau of Alcohol, Tobacco, Firearms and Explosives estimates federally licensed dealers make up anywhere from 50 to 75 percent of gun show sellers, meaning the number of private sellers could be anywhere from 25 to 50 percent. But not all booths at gun shows sell firearms. Some of those private sellers could be offering attire, accessories or knives, and not guns.
As for online sales, there's no shortage of websites listing firearms, but many of them are federally licensed dealers, meaning all those buyers still undergo a background check.
Armslist.com seems to be one of the largest websites for private sellers. It's like Craigslist for guns and boasts over 7 million visits each month. But the site doesn't list an estimate of how many guns are sold with Armslist's help.
Whether purchased with or without a background check, there's also no official estimate on the total number of guns purchased in the U.S. The closest we come is the number of background checks run on potential buyers, keeping in mind not all buyers will complete the purchase.
Supporters of universal background checks say our sales loopholes make it easier for criminals to get their hands on guns. Opponents say expanded checks will infringe on Americans' Second Amendment rights. But with our current laws, there's no way to know how many guns we're talking about.