(Jacquelyn Martin/AP)

As news of the historic extent of Orlando’s mass shooting spread, so did the “thoughts and prayers” of many politicians, an oft-heard response as these acts of terrorism become increasingly common.

The question immediately became: Would there be any action? Mass shootings had seldom led to new federal laws before. Advocates of gun control asked when the United States would finally take new steps to limit Americans’ access to guns, particularly assault rifles like the one used in the attack. Advocates of gun rights argued that more access to guns, so people could defend themselves, was the answer.

It turns out these aren’t idle arguments.

Although some Americans are likely to become frustrated with federal inaction, that’s not the complete story. A new working paper finds that mass shootings cause a sizable increase in the amount of gun control legislation proposed and passed in state legislatures.

“Mass shootings potentially lead to policy changes by focusing attention on gun violence, even if they do not provide new information or change politicians’ preferences,” write the authors, Professor Michael Luca, Professor Deepak Malhotra, and doctoral student Christopher Poliquin, all of Harvard Business School.

On net, the research shows, mass shootings result in a higher number of laws that loosen gun control rather than tighten it. “One caveat," Poliquin said in an interview, “is that we can’t say much about the magnitude of the changes in those laws.” It’s possible that the impact of one major tightening law would outweigh that of five minor loosening laws, for instance.


The study examined all state-level gun control legislation and mass shootings within the United States from 1989 to 2014. It found that a mass shooting in a state caused 2.5 more gun control bills to be proposed in its legislature’s next session, a 15 percent increase. For each additional death in the shooting (beyond the four required by their definition of a mass shooting), this figure increased by 2.5 percent.

“This does not imply that politicians and policy makers are over-reacting” in proposing all the additional bills, the authors write. It’s possible the crises “create opportunities” to alleviate gridlock and make change.

The authors compared mass shootings to the policy impact of individual homicides. A single death in a mass shooting causes the same increase in bill proposals as 66 people dying in individual homicide cases. That means the average mass shooting has the same legislative effect as a 240 percent increase in the number of homicides in a state.

And it’s not just bill introductions. Legislative sessions following mass shootings saw not only the 15 percent increase in gun control bills but a 10 percent uptick in the number of these bills enacted into law. For Republican-controlled legislatures, this means 75 percent more laws that loosen gun control restrictions. For Democrat-controlled legislatures, this means a small but statistically insignificant increase in laws tightening firearm regulations.

What can we expect out of Florida’s legislature, which is controlled by Republicans, then? The extent of the Orlando shooting was so large its impact can’t be predicted by these models; it will likely see a significant legislative response.

“Policymakers may use mass shootings as an opportunity to propose bills that are consistent with their ideology,” the authors write.

“Anecdotally,” Poliquin added, “we have seen states respond to big mass shootings with tighter laws.” At the same time, “we shouldn’t expect the politicians in Florida to suddenly change their opinions dramatically around gun control,” implying the legislature is likely to loosen gun control.

This pattern has held true historically. Connecticut’s Democrat-controlled legislature responded to the 2012 shooting at a school in Newtown by expanding its assault weapons ban, and banning high-capacity magazines and armor-piercing bullets. Texas’s Republican-controlled legislature, by contrast, passed a law allowing guns to be carried on more government properties following the 2014 shooting in Fort Hood.

As the debate surrounding gun control heats up once again, it’s unlikely that the marginal few bills will magically end the debate or make mass shootings a rarity. But our elected representatives will do a bit more than sit, think and pray.