Mass shootings are inherently difficult to study, says RAND economist Rosanna Smart. “While even one mass shooting is too many, these types of high-fatality public incidents remain relatively rare,” she says, limiting the data available to pinpoint the factors behind them and the policies most likely to prevent them.
“Even if we don’t have strong evidence to identify policy levers that are effective for reducing mass public shootings, it may be worth enacting policies that have stronger evidence for reducing more common forms of violence,” says Smart. “Those may have benefits in reducing mass shootings alongside reductions in other, broader forms of firearm deaths.”
For many in the U.S., gun ownership is an open-and-shut subject, a right that exists outside the scope of science — or oversight, for that matter. But guns, not disease, are now the leading cause of death among American children ages 1-19. According to the Gun Violence Archive, total deaths from guns exceeded 40,000 in recent years; firearm death rates reached their highest level in almost three decades in 2022.
Gun deaths and injuries are public health issues, and the last few years have underscored the risks that come from ignoring science in public health matters. For decades, pushback against federally funded research to examine the causes and remedies of gun violence interfered with progress, but since 2019 Congress has allocated $25 million annually to support such work.
A RAND Corporation initiative launched in 2018, Gun Policy in America, works to collect, review and synthesize data regarding the impacts to gun policies, “premised on the idea that the real effects of policies can be objectively determined.” RAND has just released the third edition of The Science of Gun Policy, a 500-plus-page examination of available scientific evidence of the impacts of selected state-level gun policies.
“There was only one policy for which we found even limited evidence of effectiveness for reducing mass public shootings, and that was high-capacity magazine bans,” says Smart. “While these bans won’t stop every mass shooting — California has a high-capacity magazine ban already — evidence is suggestive that they may reduce their occurrence and lethality.”
What does the available science say about gun policy? Smart is the lead author of the new RAND report, and she spoke to Governing about some of its key findings.
Governing: What was the main goal for this most recent report?
Rosanna Smart: We were hoping to synthesize existing research evidence about the effects of 18 classes of policies, primarily state-level policies, on eight outcomes that are important to decisions about gun policy.
The outcomes cover deaths and potential harms from guns as well as potential benefits from gun ownership. The overall finding is that there are a few areas where we have stronger evidence around the likely effects of gun policies.
Governing: What are some examples?
Rosanna Smart: There were three policies that we gave the highest evidence designation of “supportive evidence,” meaning there are a relatively large number of studies with consistent and precise findings about the effects of a gun law.
First, we find supportive evidence that child access prevention laws reduce firearm homicides as well as firearm suicides and self-injuries among youth. Second, we find that “shall-issue” concealed carry laws [permits must be issued to all who meet state requirements, with no further review] are associated with increased firearm homicides. We also find supportive evidence that “stand your ground” laws are associated with increased levels of firearm violence.
Those last two are more permissive gun policies largely intended to allow people to protect themselves. We find that those may actually be detrimental to public safety, having an unintended effect.
Governing: Is this just a matter of injuries resulting from self-defense?
Rosanna Smart: The size of the association between stand-your-ground laws and homicides is too large to be explained by an increase in “justifiable homicides,” or homicides perpetrated by citizens in self-defense.
Evidence for whether these laws increase feelings of safety or increase actual safety is inconclusive. That is a data limitations issue and a conceptual issue; defining “defensive” gun use can be challenging. What looks like defensive gun use to one individual may look like an attack to the person on the other side of the barrel.
Even if we agreed upon a definition, we don't have systematically collected data on the use of guns in self-defense over a long historical period.
Governing: Are there other policies that seem promising?
Rosanna Smart: There are a few other areas where we find moderate evidence. Increasing the age at which an individual can purchase a handgun tends to reduce firearm suicides among young people.
We also find that other kinds of restrictions around firearm sales and transfers, in particular requiring background checks on private sales of handguns and waiting period laws, can decrease homicides and suicides.
One other finding I'd highlight is moderate evidence that prohibiting firearm possession among those under domestic violence restraining orders can decrease intimate partner homicides.
A graphic from RAND's Gun Policy in America project reflects current evidence regarding polices that are likely to decrease (brown lines) or increase (green lines) unwanted effects from firearms. The thicker the line, the stronger the existing evidence from studies.
Governing: Are you seeing any shift in attitudes about gun policy?
Rosanna Smart: I do think there's a lot more interest and a lot more openness to considering a variety of regulations aimed at reducing gun violence.
The rising rates of gun violence during the COVID-19 pandemic have exacerbated trends that have occurred since 2014. Guns are now a leading cause of death among youth aged one to 19; this comes up with mass shootings in particular.
Together, these are galvanizing public interest around gun policies and finding effective strategies to reduce gun violence.
Governing: Are there any policies moving forward that run contrary to available evidence?
Rosanna Smart: The finding that there's relatively strong evidence that “shall issue” concealed carry laws increase firearm violence is a particularly notable in light of the Supreme Court's decision last summer in New York State Rifle and Pistol Association vs Bruen. That decision effectively ruled that states that had more restrictive policies than “shall issue” states had to move toward the more permissive “shall issue” policy regime.
This suggests that many of these states may face issues with worsening firearm homicides unless they're able to kind of adopt other regulations that might help buttress against potential threats to public safety.
There's also been a move outside of that Supreme Court decision toward permitless carry laws. It will be very important to try to evaluate and understand the effects of those even more permissive concealed carry regimes on public safety.
Governing: How much work has been done to evaluate the effects of combinations of policies?
Rosanna Smart: That’s an area our team is delving into; one thing that we've tried to do in our own empirical research is to recognize that any single policy might not have a very large effect. It may be more constructive and instructive to evaluate the joint effects of policies.
Our research, and the research of others who have started to move into this space, is finding that one is able to have more confidence around the effects of a given set of laws if they're examined as a joint construct versus as singular policy variables.
(Kaiser Family Foundation)
Rosanna Smart: I don't know if I can put a dollar value on it. That $25 million is at least a move in the right direction. There are private philanthropies that stepped up and filled gaps during the dearth of federal funding and have continued to invest. The $25 million is a lot of money, and it may be sufficient to do smaller-scale secondary analysis [new research using existing data] of the effect of specific policies on specific outcomes.
But there are a lot of fundamental questions about gun violence and gun policy that we don't have answers to that require large-scale investments. If you're going to design, implement and evaluate kind community-level interventions, those need more money.
Governing: Are there other gaps?
Rosanna Smart: It continues to shock me that we don't know how many people in the U.S. are non-fatally injured by firearms. To build a data infrastructure to measure that and to sustain that measurement going forward, so we can understand what works in reducing non-fatal as well as fatal gun injury, requires an order of magnitude greater than what we're seeing.
It's a very complex problem. We've done some work looking at hospitalizations for firearm injury, but you have to coordinate across different hospitals and different state systems to try to get an estimate. To move beyond those to firearm injuries that don't require hospitalization requires additional resources.
Governing: Are there ways that public discussions of gun policy routinely miss the point?
Rosanna Smart: There is a tendency in this policy area — and I'm sure it occurs in others — to speak with more certainty than the science supports. This happens both with people who are saying we need to tighten up our gun laws and with people who are saying we need to relax them.
I wish there was more nuance. I wish everyone would write a 500-page report when writing a media article. We could bring in a little more humility and a little more acknowledgment that we're not going to be a hundred percent certain about what would prevent singular incidents from occurring, or what would eliminate gun violence.
One other area is the framing around mass shootings. Those tend to galvanize public attention and the desire for policy action in ways that other incidents of violence don't.
(RAND Corporation)
I would like to see more focus on recognizing the problem of gun violence broadly, and the communities it affects on a daily basis and thinking about broader, more comprehensive solutions that can prevent mass shootings and also the more common forms of gun violence that people experience in their everyday lives.
Governing: Is it a challenge just to get people to agree that science can tell us something about gun policy?
Rosanna Smart: It’s easy for me to be pessimistic. There are always going to be people who have their perspective on the effects of gun policy, or what they want their gun policies to look like, and are not interested in what the science says.
I don't expect them to read the report and change their minds. The goal is — as an objective, neutral player — to lay out what we know and what we don't know, the areas where maybe we're starting to learn something and where we could stand to learn more.
The broader goal of the Gun Policy in America project is to establish a set of shared facts. We're not going to impose values or say that one thing should be done versus another, but we can at least try to bring a shared sense of scientific understanding to this important policy question.
Governing: Would “We’ll base policy on science” be the policy most essential to better outcomes?
Rosanna Smart: Good luck getting that passed!
Governing: Any last thoughts?
Rosanna Smart: There is one more thing I want to flag. The areas where we have the strongest evidence relate to the effects of these policies on deaths.
But if policymakers are considering enacting more restrictive policy regimes, there's a need to think carefully about how those restrictive laws are implemented and enforced.
How can we implement laws in a way that maximizes benefits but reduces potential harms that might derive from enforcing restrictions? We certainly don't want to exacerbate costs to communities and populations that already bear a disproportionate share of the burden of gun violence.
Editor's note: This article was updated on Jan. 24, 2023, to include recent mass shooting events.
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