Whenever there’s a shooting like the one near New York’s Penn Station earlier this week, the gun control debates rise back to the surface. Proponents for stricter laws have argued that heavier gun control means fewer shootings, and they might have a point. Well, at least for mass shootings.

A study by the Everytown for Gun Safety, a gun violence prevention group supported by former New York City Mayor Michael Bloomberg, revealed that states with background checks saw 52% fewer mass shootings than those without that requirement. Per the Huffington Post, the organization studied 133 mass shootings that occurred in the U.S. between January 2009 and July 2015 to get their results, and the shootings were defined by a criteria of at least four individuals killed by gunfire. Additional findings showed that states with mandatory background checks saw 63% fewer mass shootings committed by individuals who were unable to legally own a gun, and 64% fewer domestic-violence involved mass shootings.

Federal law requires licensed gun dealers to perform criminal background checks but some individuals have found a loophole by purchasing guns online or through a private seller. There are 18 states, plus the District of Columbia, that combat this by requiring background checks for all handgun sales, including on online purchases and those bought at gun shows. 

“State laws have been shown to have an influence on rates of gun violence in a pretty voluminous body of research," Ted Alcorn, research director at Everytown of Gun Safety, said. "When we see a state law that prevents people from buying a handgun without a background check at a gun show or online market, and we see a lower rate of mass shootings as a result, I think it’s fair to draw the conclusion that they may be related."

While background checks might help reduce the number of shootings, Alcorn maintains that gun violence isn’t completely unavoidable. "No single policy, be it background checks or otherwise, is going to prevent every future act of gun violence," he added. "But it is clear in so many dimensions that this is a critical, central piece of public safety legislation that has a real impact on people's lives."