In Chicago, as in so many American cities, it’s hard to imagine a more intractable public policy problem than gun violence. But University of Chicago Professor Jens Ludwig, 56, cofounder and director of the school’s Crime Lab, delivers some hope in his groundbreaking new book, Unforgiving Places: The Unexpected Origins of American Gun Violence. Based on a wealth of scientific data on decision making by violent criminals and his own fieldwork in Chicago, he offers social policy strategies for transforming neighborhoods into safer spaces.

What gave you the idea in 2007 to start the Crime Lab?

There was a doctoral student in chemistry at the University of Chicago named Amadou Cisse. That fall, about two weeks after he defended his dissertation, he was shot and killed about a block off campus. That led to a lot of conversation about how a university can be more helpful to our home city and to cities more generally. How do we nerds who specialize at looking at data make the world better? The answer we came up with is that government is really the 800-pound gorilla. The City of Chicago spends close to $20 billion a year, the state more than $50 billion, and the federal government trillions. Could we, as a research and development partner, help the public sector to spend its money in as socially effective a way as possible?

A major case study in your book compares gun violence rates in Greater Grand Crossing with those in South Shore, which is a more commercially vibrant area.

They’re two neighborhoods right across the street from one another on the South Side. The level of poverty and racial segregation is exactly the same. But Greater Grand Crossing has twice as many shootings per capita. Why is that? One of the things I point to is something [social theorist] Jane Jacobs noted 60-plus years ago: eyes on the street. It’s really important to build neighborhoods that mix the commercial with the residential. When you have that, you have people walking around. You’re going to get pizza for dinner with your family. You’re going to the hardware store to get some nails. And Jane Jacobs could see that was strongly correlated with the rates of violence.

I was surprised when you wrote that, unlike with robberies, only 20 percent of acts of gun violence are for material gain.

Yep, I was surprised the first time I saw the data, too. We’re used to thinking about gun violence from The Wire, where Snoop and Chris Partlow are going to do a hit over some drug-selling turf. But most shootings in Chicago and other cities are not motivated by economic considerations, and they’re not premeditated. They are lively, in-the-moment arguments that veer sideways and end in tragedy because someone’s got a gun. The motivation is fleeting, though. And if you had someone around to step in and de-escalate the situation, then you can prevent the shooting from happening. A few years ago in South Shore, a 17-year-old named Kalvin Carter shot and killed a 16-year-old named Jamal Lockett in an argument over a used bike that might perhaps fetch $50. It’s hard to make sense of someone being willing to risk a long spell in prison, which Carter is now serving, for such a trivial gain. It’s much easier to imagine that Carter’s fast-thinking self led him to conclude, Literally nothing is worse than letting this guy make me look like a coward in front of all my friends. The question for public policy is, How do we give the slow-thinking self a better chance of stepping in?

In the book, you describe the limits of conventional approaches to reducing gun violence. From the left, the strategy has been to try to address root causes of poverty and desperation, which, of course, is a slow process. And from the right, it’s been “lock ’em up,” with incarceration rates skyrocketing.

The “lock ’em up” trend in the United States started in the 1970s around the time people became skeptical that crime prevention was possible. It wasn’t a crazy perspective given what we knew in the ’70s. The prevention we’d been trying was focused on the slow-thinking rational mind: “If we get people a better job that will incentivize them to not get thrown in jail, that will be our solution.” There’s lots of evidence to suggest it totally works for preventing property crime, but not so much for violent crime. Also, there’s good evidence now to suggest that really long prison sentences are not a very good return from a public safety perspective. The difference between a 40-year sentence and a 30-year sentence, that extra 10 years, does not do much to deter more shootings. Let’s take the money that we save there and pour that into some kind of evidence-based prevention program.

You write that both New York City and Los Angeles have gotten their gun violence rates down significantly using programs based on principles of behavioral economics.

What those cities were the first to do was look at the data and see if we can find out when and where the gun violence is most likely and then try to concentrate our police resources there. One example here in Chicago: There’s a liquor store on the South Side that stays open later than most. All of a sudden you have people from different neighborhoods and different gangs who are liquored up congregating in the same place. You can look at the data and see, Oh, at that spot there’s always shootings at 3 or 4 in the morning. Maybe we put a cop there. Maybe we ask the liquor store to hire extra security for that time. Maybe we ask the liquor store to close at the same time as the others. The second thing Los Angeles and New York City did: They were early and rapid adopters of community violence intervention. These are community nonprofits that try to figure out when and where shootings are going to happen and basically mediate that. Some of these programs also work with people in advance of conflicts to teach them how to navigate these situations. Both strategies hold real promise.

You think that relieving gun violence can also uproot fundamental causes of poverty.

Exactly. The city gave millions of dollars to Whole Foods to open a store in Englewood. But it’s very, very hard to get people to go to Englewood to shop at Whole Foods when they’re worried about the gun violence. That illustrates that gun violence is a huge headwind for community development, economic development. And so I have come to think of gun violence as the social problem that sits upstream of almost every other social problem facing Chicago and other American cities. If you can get the gun violence under control, you can have neighborhoods that are thriving, that people and businesses are moving into. That creates tax revenue that then helps you do all the other things you want to do: fix the schools, strengthen the social safety net, strengthen the mental health delivery system, improve infrastructure, and on and on. We spend a lot of time in the United States appropriately worried about inequality of income and wealth. We don’t spend nearly enough time worrying about inequality in something even more fundamental, which is public safety.

Beyond data, you illustrate the problem with scenes from your ride-alongs with Chicago police. What did you learn from that?

How fragile and vulnerable the human body is to firearm violence. The first time I saw someone who had been shot, it was in a back alley in Garfield Park. It really does change you to realize that we are just walking around unprotected against these insanely high-velocity metal projectiles that we’ve made very easy for people to fire against one another. Intellectually, I obviously know it, but when you see a human being lying in a back alley in Garfield Park, it just hits you viscerally.