Let’s cut to the chase: “The overwhelming majority of murders in the United States involve guns,” says economist Jens Ludwig. “And in fact, most of the difference in overall murder rates between the United States and other countries are due to murders with guns.”

This may seem intuitively obvious to outside observers, but studying guns within the United States has long been a fraught endeavor, and the amount of research isn’t commensurate with the impact on U.S. society. That said, Ludwig has taken on exploring the roots of American gun violence, work that serves as grist for the Crime Lab he directs at the University of Chicago and for many of his books, including his latest, Unforgiving Places: The Unexpected Origins of American Gun Violence. What’s he’s found is that the folk wisdom around gun violence doesn’t rally hold up to the evidence.

In this Social Science Bites episode, he explains to interviewer David Edmonds how – using insights about ‘system one’ and system two’ thinking developed by Daniel Kahneman – cognition in individuals has more explanatory power than traditional variables like poverty, education and environment.

“I think system one plays an underappreciated role in all interpersonal violence, all of the issues, and this way of seeing what is driving violent behavior among people is equally true for knife violence in the UK and on and on,” Ludwig says. “So I think this is really a universal thing about people’s behavior. This sort of frame on the problem helps make sense of a bunch of patterns in the data.”

Ludwig is the Edwin A. and Betty L. Bergman Distinguished Service Professor at the University of Chicago, Pritzker Director of the Crime Lab and codirector of the Education Lab at that campus, and codirector of the National Bureau of Economic Research’s working group on the economics of crime.

He and his labs are routinely recognized for their work. The Crime Lab in 2014, for example, received a MacArthur Award for Creative and Effective Institutions, while eight years earlier Ludwig himself was awarded the Association for Public Policy Analysis and Management’s David N. Kershaw Prize for Contributions to Public Policy by Age 40. Some of the books he’s co-authored or co-edited include 2000’s Gun Violence: The Real Costs, 2003’s Evaluating Gun Policy, and 2012’s Controlling Crime: Strategies and Tradeoffs.

To download an MP3 of this podcast, right-click this link and save. The transcript of the conversation appears below.

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David Edmonds: The United States is a gun crime superpower, In the Midwest City of Chicago, the murder rate was down considerably in 2024 — fewer than 600, most of them from guns. Still, the number was about the same as for the whole of the United Kingdom. What explains American gun violence? Jens Ludwig runs the University of Chicago’s Crime Lab and is the author of Unforgiving Places: The Unexpected Origins of American Gun Violence. Jens Ludwig, welcome to Social Science Bites.

Jens Ludwig: Thank you so very much for having me on. This is terrific.

David Edmonds: We’re talking today about killing, and in particular, killing with guns. Violence with guns. You’ve been researching this for years. Tell us about the scale of the problem in the United States.

Jens Ludwig: The United States is a massive outlier with respect to murder rates per capita compared to any other rich country in the world. So our murder rate has fluctuated over the last several decades between five and 10 per 100,000 that’s tens of thousands of people killed every year. On a holiday weekend in Chicago, long holiday summer weekend, there might be 50 or 60 people shot. Our murder rate is multiple, multiple times what you would see in the United Kingdom or in a country like Japan, substantially higher even than what you would see in a country that you don’t think of as being particularly well run, places like Turkey. We’re just unimaginably off the charts.

David Edmonds: And what percentage of homicides involve guns?

Jens Ludwig: The overwhelming majority of murders in the United States involve guns. And in fact, most of the difference in overall murder rates between the United States and other countries are due to murders with guns.

David Edmonds: OK, so you’ve talked about the US being an outlier when it comes to gun violence. Is that true of other types of crime as well, for example, like burglary?

Jens Ludwig: If you compare, for example, the United States to the United Kingdom, the US is much less of an outlier with respect to almost every other sort of non-gun crime — burglary, robbery, assaults, that sort of stuff. And I think another way to sort of see that it’s not something that’s fundamentally different about people in America is that the rate at which people kill each other through means other than firearms in the United States, on a per capita basis, isn’t really all that different from the UK. The real American exceptionalism here is murders with guns.

David Edmonds: OK, so let’s get to the root cause of this, or the root causes, perhaps. The obvious cause is that guns are just a lot more readily available. The US is not like the UK, where it’s very difficult to get hold of a gun here. Now I’m guessing that this is not the only answer, otherwise there wouldn’t be much for you to research. But tell me why the answer isn’t just as simple as I’ve made out.

Jens Ludwig: Yeah, let me start off by acknowledging the first part of the question, which the data suggests, is very true, that the 400 million guns that the United States has for a country of 330 million people is without question part of the story. You know, we have state level data on a proxy for household gun ownership. And we can see that over a decades-long period, the household gun ownership rate between the northern part of the United States the southern part of the United States have been converging over time, and we can see over that same time period that murder rates have been converging across these regions as well. So it’s a nice sort of natural experiment that points to something that’s suggestive of a causal relationship between overall gun availability and murders. And so, if you had a wand that one could wave, that would get rid of the 400 million guns in the United States, I think it is very much true that the United States would become much, much safer. But as you say, that’s not the whole story.

David Edmonds: America is not the only country awash with guns. My elder brother lives in Switzerland, where almost everybody has a gun, but they don’t have the murder rate that you have. So it seems like guns alone can’t be the answer.

Jens Ludwig: Yeah, gun violence is really the product of two things, not just one thing. My little cartoon equation for this in the book is gun violence equals guns plus violence. What you can see in the data is that, for instance, that Switzerland and Canada have almost identical levels of gun ownership, and yet, the murder rate in Canada is multiple times what you see in Switzerland. And I think the explanation there is that the rate of violent crime is substantially different between Switzerland and Canada. And so I think what the data seemed to suggest is that guns don’t cause violent behavior, cause violent crime. Guns make the violence that happens much more deadly. So you can have lots of guns and not many murders, lots of violent crime without guns and not many murders, but if you have lots of guns and lots of violence together, that’s the thing that leads to lots of murders.

David Edmonds: So it’s guns plus something, and the key question is, what is the something? And let me propose an answer, and then you can tell me whether this is right. Again, it seems like there’s an obvious answer. It’s guns plus poverty, or guns plus single-parent families.

Jens Ludwig: You know, the high-level idea that sits over all of this is it’s guns plus violence, equals gun violence. And so then, as you’re driving at the natural next question is, so what is it that is driving violent behavior across countries, across different places, within countries, across people? For hundreds of years, social scientists have thought that poverty was a very central feature of the entire crime problem. What you see when you really look closely at the data is that’s a little too simple. The best sort of natural experiment, research in economics, suggests that changes in people’s incomes change in people’s employment status, social programs that put more money into people’s pockets, do indeed reduce people’s involvement in property crime, but don’t change people’s rates of involvement in violent crime. We have mayors in the United States who say things like, “Violence is the expression of poverty. We’re never getting rid of the violence problem until we get rid of poverty.” And I think that is not what th