America has around one mass shooting, defined as at least four people shot, per day on average. But for a few days this month, when some 80,000 gun owners descend on Dallas for the annual National Rifle Association convention, that gun injury rate may drop.

That’s because the convention has historically coincided with a temporary dip in gun-related injuries, according to a new analysis published in the New England Journal of Medicine.

To come to that conclusion, researchers from Harvard Medical School and Columbia University used an insurance database of nearly 76 million claims to tally emergency department visits and hospitalizations related to firearm injuries on NRA convention dates, and during identical control days in the three weeks before and three weeks after the meeting, from 2007 through 2015.

They then estimated the rates of firearm injuries for both the NRA convention dates and the control dates, hoping to test common assumptions: that gun injuries often occur among inexperienced users, and that gun safety increases with experience and training. Groups that oppose gun control, like the NRA, often assert that education is key to keeping injury rates down — and that guns are totally safe when handled by people who know how to use them.

If that were the case, the researchers expected that the gun injury rate would hold stable or even rise during NRA conventions, when thousands of very experienced and heavy gun users were holed up in meetings.

Instead, they found the opposite seemed to be true: The gun injury rate fell by nearly 20 percent nationwide during NRA conventions. More precisely, on convention dates, the national gun injury rate was 1.2 per 100,000 — compared to 1.5 per 100,000 during the control dates. In the states hosting the conventions, the drop was even more dramatic — from 1.9 to 0.7 per 100,000.

The lead author of the study, Harvard Medical School professor Anupam Jena, told Vox in an email that the tumbling gun injury rate during the NRA convention is the result of “a brief period of abstinence in gun use.” Gun owners are away at the convention, and venues where guns are commonly used — like ranges or hunting grounds — are also temporarily closed while staff are at the convention.

“The implication of the study is that even among presumably experienced gun users there are safety risks associated with gun use,” he added in an email. “Guns don’t become safe simply through training and experience alone, as gun enthusiasts often argue.”

Members of the public health community have embraced the paper, with one Emory University epidemiologist even cheekily suggesting that one way to improve gun safety in America would be to make NRA conventions last the entire year:

Consequentialist epidemiology in the @NEJM



I can think of a fantastic public health intervention -- let's make the @NRA annual convention a year-long affair. Everyone else in the country would benefit enormously.https://t.co/pnmeNqIj9e — Alvaro Alonso (@alonso_epi) March 1, 2018

In America, there has long been a strong correlation between gun ownership and gun violence.

As Vox’s German Lopez has written, the US is a global outlier when it comes to gun ownership. “Estimated in 2007, the number of civilian-owned firearms in the US was 88.8 guns per 100 people, meaning there was almost one privately owned gun per American and more than one per American adult. The world’s second-ranked country was Yemen, a quasi-failed state torn by civil war, where there were 54.8 guns per 100 people,” Lopez writes.

Put another way, Americans account for less than 5 percent of the world’s population and own 42 percent of the world’s privately held firearms.

Researchers have found ample evidence that widespread gun ownership is directly linked to America’s unique gun violence problem: States with more guns, in particular, tend to have more gun-related deaths. In a new analysis from the RAND Corporation, researchers found that more restrictive laws lead to fewer gun deaths, while more permissive laws are linked with more gun deaths.

The NRA hasn’t yet responded to Vox’s request for comment about the paper, but an NRA spokesperson told CNN she was skeptical of the findings.

“A quick glance at the numbers says it all,” said Jennifer Baker, the NRA’s director of public affairs, in a statement. “There are 100 million gun owners in America, with about 80,000 of them attending the NRA annual meeting each year — that’s less than one-tenth of 1 percent of American gun owners.” Baker said it didn’t make sense that the firearms injury rate would plummet 20 percent when “less than one-tenth of 1 percent of gun owners attend this event.”

The study was observational, not experimental, so the researchers couldn’t prove the convention caused the decline. And Jena, the NEJM study author, said it’s possible the 20 percent average estimated reduction is too high. In the study, their confidence interval ranged widely, from 6.7 to 34 percent, meaning the decline in gun injuries could be smaller or larger than 20 percent — but he noted that it always trended in the direction of a decline. He added that the conference may have an outsize impact because the people likely to attend are probably among America’s heaviest gun users.