Chris Blattman is an economist and political scientist at the University of Chicago, but he’s not the type to dwell in an ivory tower working purely on theoretical questions. Instead, he does empirical work that gathers data from the real world — which then influences the real world in turn.

His recent research focuses on violence, asking questions like: Why do people fight? How can we reduce the chance that criminal violence or war will spring up or stop it once it has?

He’s explored these questions in far-flung communities, from drug gangs in Colombia to child soldiers in Uganda to criminals in post-war Liberia. And this year he brought together his findings in a new book, Why We Fight.

One study that Blattman and co-authors ran in Liberia deserves special mention. It recruited 999 of the most dangerous men in the capital city of Monrovia off the street. The men were split into four groups. Some received cognitive behavioral therapy, while others got $200 in cash. Another group got the therapy plus the cash. Finally, there was a control group that got neither.

The positive effects on the therapy-plus-cash group were stunning: crime and violence fell by about 50 percent. This held true not just a year after the intervention but 10 years later, indicating the cash and therapy approach could have truly lasting effects.

Blattman estimated that there were 338 fewer crimes per participant over 10 years. Given that it had cost just $530 per participant to implement the program, that worked out to $1.50 per crime avoided. It was a pretty amazing deal, and it provided compelling evidence that offering at-risk men therapy plus cash reduces the future risk of violence.

The program in Liberia has inspired a similar but more intensive program called READI in Blattman’s backyard: Chicago. Over 18 months, men in the city’s most violent districts participate in therapy sessions in the morning followed by job training in the afternoon. The rationale for the latter is that in a place with a well-developed labor market like Chicago, the best way to improve earnings is probably to get people into the market, whereas in Liberia, the labor market is much less efficient, so it made more sense to simply offer people cash.

A lot of Blattman’s earlier work focused on finding the most effective ways to alleviate poverty in developing countries. In particular, he studied unconditional cash transfer programs — giving poor people money, no strings attached — at a time when that idea was viewed skeptically by experts.

It was a skepticism Blattman initially shared.

“I started off like many people, 10 to 12 years ago, never having thought seriously about people getting cash as a development intervention and thinking it was vaguely crazy or irresponsible,” Blattman told Vox a few years ago.

Then he ran some randomized controlled trials in Uganda. When he tracked the long-term impact of giving cash to Ugandan youths, he found that four years after the intervention, they were working more and earning more than a control group.

But Blattman has also complicated our understanding of the power of cash transfers, showing that they’re no panacea. In a follow-up study with the Uganda youths, he found that by year nine, the control group had caught up to the youths who’d been given the cash. The findings suggested that cash transfers aren’t necessarily what all poor people need to escape poverty, but they do speed up people’s escape from poverty — a huge good in itself.

Today, findings like these influence the top nonprofits trying to find the best way to alleviate global poverty, from BRAC (which gives cash plus other kinds of help) to GiveDirectly (which has traditionally given cash and is now considering adding other kinds of help into the mix).

Over the past couple of decades, the hugely important project of alleviating poverty has become less guesswork, more science. Blattman’s empirical research has contributed meaningfully to that body of research — and meaningfully to the people in the real world.