There’s something strange happening with violent crime in America. Incidents are reaching levels they haven’t hit in decades, and nobody seems to know why. But, to go even deeper, what causes violent crime to happen at all—and what can be done to help prevent it? Prof. Jens Ludwig is an economist and urban policy expert at the University of Chicago and the Pritzker Director of the Crime Lab, which partners with policymakers in major cities across the country to help reduce gun violence and reduce the harms of the criminal justice system itself. Using randomized control trials and massive data sets, he and his colleagues have been able to find demonstrable policy strategies and community programs for preventing crime.