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In the wake of two mass shootings in the past two weeks (one in Atlanta at massage parlors, and one in Boulder Colorado at a supermarket), President Biden called for the assault weapons ban to be reinstated. Texas Senator Ted Cruz, a Republican, objected, calling gun control legislation “ridiculous theater.” We test whether the ban worked or not.

“So, did the previous “assault weapons” ban work?” asks the Investor’s Business Daily. “It turns out that various independent studies came to the same conclusion: the ban had no measurable impact on the number of shootings or the number of shooting deaths while it was in effect.

They cite data from the 2005 National Research Council and the 2004 National Institute of Justice.  But what about after the ban lapsed in 2004?

My students (Tia Braxton, Porter Law, Yasmin Roper, Damir Rosencrants, Caleb Tyler, Andrew Valbuena) and I did just that, testing to see if the assault weapons ban had any impact on the number of mass shootings.

We used Statista’s Research Department list of annual mass shootings, which began in 1982 and continued through 2021, though we had to add the Boulder case to this year, as their data ended March 17, 2021.

We found that when comparing the years before the assault weapons ban and during the ban, there’s little difference between the number of mass shootings in both timeframes. From 1982-94, there were an average of 1.4615 mass shootings per year, and 1.6 mass shootings per year during the AWB years, 1995-2004, when the ban expired.

But it was a different story when we covered the years after the ban. From 2005 to 2021, there were an average of 5.1176 mass shootings per year, far more than the 1.6 from the AWB years, and our year isn’t over yet. And yes, the difference in means was statistically significant.  Lumping the non-ban years with the ban years shows more mass shootings, on average, per year, during the years without an assault weapons ban, than the years with an AWB.

This explains the numerous columns claiming that the ban didn’t work. Studies from 2004 and 2005 wouldn’t find much difference before and during the ban, when we didn’t have a post-ban to compare to. And we confirmed their research on that part of the study. But you’d think that columns written in 2018 and 2019 would update their numbers.

The highest number of mass shootings in a year before the ban was four, while there were five in 1999.

Since the ban lapsed there have been more five mass shootings in a year six times, with 11 in 2017, 12 in 2018, and 10 in 2019, according to the data from the Statista Research Department.

Using cases with fewer deaths shows striking results. Teo Armus with The Washington Post reports “There were 615 mass shootings in 2020 that fit the inclusion criteria of this article, resulting in 521 deaths and 2,541 injuries, for a total of 3,062 victims. Compared to the previous year, there were 181 more incidents.” And that’s more killings in a year marked by the pandemic, and many sheltering indoors.

No doubt, there will be critics from both ideologies who will argue we have to change the number of casualties, or narrow a focus to a certain type of gun, or want to look at different years. We welcome those additional studies, contributing to the larger body of knowledge.