A new study by Everytown for Gun Safety found states that require background checks for all handgun sales were 52 percent less likely to have a mass shooting.
The survey found that between January 2009 and July 2015 there were 133 mass shootings in the United States. A mass shooting is defined as any incident where at least four people were murdered with a gun, according to the FBI.
In states where background checks are required, 37 mass shootings took place during the surveyed time period.
There were 96 mass shootings in states that do not require a background check or have loopholes around the law to purchase a handgun.
Background checks are required by federal law but people can find loopholes around this requirement by purchasing firearms online or at gun shows, The Hill reports.
There are a total of 18 states who have closed these background check loopholes.
The study also found that mass shootings by people prohibited from possessing firearms were less likely by 63 percent in states that require background checks.
There were 44 mass shootings committed by people prohibited from owning a firearm in the surveyed period; 10 in states that require background checks and 34 in states that do not.
Domestic Violence mass shootings were also notably lower in states with background checks, being 64 percent less likely to happen than in those that do not have the requirement.
“This is just the latest piece of evidence that Americans are safer from gun violence in states where a handgun buyer must pass a criminal background check before buying the firearm,” Everytown Research Director Ted Alcorn said in a statement obtained by The Hill. “We already know that closing the loophole that allows guns to be sold without background checks online and at gun shows is an essential component to reducing gun violence."