Making gun buyers wait a few days before receiving a newly purchased firearm could keep 910 people across the US from being killed with a gun each year, a new study says. The research supports enacting a nationwide waiting period between buying and receiving a gun; in the states that already do this, guns appear to be killing fewer people.

The recent mass shooting in Las Vegas that killed 59 people is a wrenching reminder that every year, roughly 33,000 people in the US are killed by guns. That’s as many as people killed by car crashes, and it’s a bigger proportion than in any other developed country. A team of researchers at Harvard Business School wanted to find out whether making people wait before putting a gun in their hands put a dent in those numbers. It did: gun killings in states with waiting periods dropped by 17 percent, and suicides by between 6 and 11 percent, according to results published Monday in the journal Proceedings of the National Academies of Science.

The analysis is “state of the art,” says Jeffrey Swanson, a professor in psychiatry and behavioral sciences at Duke University who was not involved in this study. Luis Amaral, who studies social systems at Northwestern University, called the findings “robust” in an email to The Verge. And the results are clear, they agree. “There’s also, this article says, a cost to society in allowing people immediate access to a gun when they might be in a moment when they’re inclined to do something harmful,” Swanson says.

The rationale behind waiting periods, the study says, is that someone in a fit of depression or rage who’s bent on doing harm to themselves or others might lose steam if they can’t get a gun immediately. These cooling-off periods wouldn’t actually prevent anyone from getting a gun in the end, but they might deter people who could have otherwise passed a background check — like people with angry, impulsive behavior who are prone to violent outbursts, for example, Swanson says. “Many people like that are not prohibited from buying guns,” he says, but they can be delayed. “This cooling-off period, if you scale that up, you could save lives.”

To find out exactly how many lives, Harvard Business School graduate student Christopher Poliquin and his team analyzed gun violence in the 44 states that enacted waiting periods for some amount of time between 1970 and 2014. They compared gun deaths in states before and after a waiting period was enacted to gun deaths over those same years in states without waiting periods. They found that waiting periods cut down on suicides by gun by about 7 to 11 percent, and gun homicides by 17 percent. That added up to a drop of 750 gun homicides in 2014 — the most recent year the team could get data on gun deaths. If the policy were to go nationwide, it might stop 910 gun homicides in the United States each year.

The research team then studied the effects of a 1993 law called the Brady Handgun Violence Prevention Act. Rolled out in 1994, it required licensed gun retailers to conduct background checks on people purchasing firearms (in states that weren’t already doing so), and gave retailers a five-day waiting period to conduct the checks. This gave Poliquin and his team a way to analyze the effects of waiting periods without the possibility that the states that chose waiting periods were already different from the ones that didn’t. They found a 17 percent drop in the number of gun homicides, and a 6 percent drop in gun suicides in each state that started waiting periods because of the Brady Act. The new findings are more accurate than a previous study on the Brady Act, which incorrectly included states that weren't affected by the law in its analysis.

The research is already having an impact on policy; Poliquin says that after speaking with one of the study’s co-authors, Rep. Raja Krishnamoorthi (D-IL), introduced a bill that would require a three-day waiting period for handgun sales nationwide. “It’s pretty cool to be able to see an immediate reaction from policy makers when you do research. It’s the best outcome with research like this,” Poliquin said, before catching himself: “Well, I guess that the best outcome would be to have the policy actually change.”