Gun control is one of the most sharply divisive issues in the U.S. today. Federal laws have many loopholes regarding who may buy or own a gun, and state laws vary widely. In January, President Obama outlined his strategy to curb gun violence. However, with a change in administrations on the horizon, a strong gun lobby and equally strong opinions, it's more likely that America will be fighting about gun control for a long time.
Here are some facts about the state of gun control in the U.S.:
2. The U.S. ranks first globally in gun ownership per capita, with about 89 firearms per 100 residents. It is followed by Yemen at 54 and Switzerland at 45 firearms per 100 residents.
3. The South is largely more violent than the rest of the country.
Most checks are determined within minutes, but if the three-day deadline is missed, the sale may legally proceed.
4. The National Instant Criminal Background Check System (NICS), launched by the FBI in 1998, determines whether a person may buy guns or explosives.
5. The FBI has three days to approve a sale by a federally licensed firearms dealer. Most checks are determined within minutes, but if the three-day deadline is missed, the sale may legally proceed.
6. The vast majority of guns used in 15 recent mass shootings were bought legally and with a federal background check.
7. The NICS does not require background checks in sales between private parties. About 40 percent of all firearms sold in the U.S. are obtained this way.
In 2015, the NRA spent nearly $3.6 million on lobbying efforts.
8. More than half of the gunmen in the past 15 recent mass shootings had criminal histories or documented mental health problems that did not prevent them from obtaining their weapons.
9. The most common illness associated with mass public shootings was paranoid schizophrenia, a type of schizophrenia in which the person has delusions of being plotted against or persecuted.
10. The 10-year Federal Assault Weapons Ban, which expired in 2004, prohibits the sale of some semiautomatic weapons for civilian use. There have been multiple attempts to renew the ban, but none have succeeded.
11. However, in the U.S., handguns were used more often in mass shootings, at 47.9 percent, compared with 24.6 percent of mass shootings involving assault weapons.
States with tighter gun control laws appear to have fewer gun-related deaths.
12. Federal law prohibits handgun ownership by any person under the age 18, but there is no minimum age for long gun (e.g. rifle and shotgun) ownership. It's technically legal for a child to possess a long gun in 30 states.
13. Overall, about a third of all Americans with children under 18 at home have a gun in their household, including 34 percent of families with children younger than 12.
14. Of the homes with children and firearms, 55 percent keep one or more firearms in an unlocked place.
15. Though many mass shooters share an affinity for violent video games, studies are inconclusive as to whether those games inspire real-life shootings. In 2001, the 6th U.S. Circuit Court of Appeals ruled that it was "simply too far a leap from shooting characters on a video screen to shooting people in a classroom."
16. While blacks are significantly more likely than whites to be gun homicide victims, blacks are only about half as likely as whites to have a firearm in their home (41 percent vs. 19 percent.)
21. Mass shootings don't appear to alter Americans' views on gun control. The Pew Research Center reported in 2014 that for the first in more than 20 years, Americans showed more support for gun rights than gun control.