A study claims to have new evidence that proves tighter gun control laws can reduce gun violence. After the repeal of a 2007 Missouri law — a law that required potential gun buyers to be vetted and licensed by a local sheriff — Researchers in Missouri tracked changes to the homicide and non-negligent manslaughter rates.

The report, soon to be published in the Journal of Urban Health, analyzed the data and found there was immediate spike in gun violence and murders, with more than 60 additional gun-related murders per year in Missouri between 2008 and 2012.

“Coincident exactly with the policy change, there was an immediate upward trajectory to the homicide rates in Missouri,” Daniel Webster, one of the lead authors of the study, told the BBC. Webster is also the director of the Johns Hopkins Center for Gun Policy and Research. He believes that the study confirms that strict firearm laws lead to less gun deaths.

Many states have worked to tighten their gun control laws after the December 2012 shooting at Sandy Hook Elementary School in Newtown, Conn., but gun and ammunition sellers reported sales had been increasing throughout the past two years. Sellers attributed the spike in gun sales to President Barack Obama’s re-election, CNN reported. Obama spoke out against assault weapons during his 2012 presidential campaign and continued to push for stricter gun control regulations into his second term. Gun sales spiked again after the shooting in Newtown, Conn.

Unlike 2013, guns sales have plummeted in the first few weeks of 2014. According to a CNN Money report, gun industry analyst Rommel Dionisio said, “Retail (gun) inventories, which had been in short supply last spring, have largely returned to normal now.” Outdoor-gear retailer Cabela’s Inc. reported gun and ammo sales were down 50 percent from this time last year. FBI background checks are also down about one-third from January 2013.

The Congressional Research Services estimates that there are over 300 million guns in circulation in the United States.