Do immigrants drive down wages, do minimum wage increases reduce job opportunities, and do people who did well in school earn more money? These are questions that the winners of the 2021 Nobel Memorial Prize in Economics looked to the world around them for answers to. David Card, Joshua Angrist, and Guido Imbens developed ways of interpreting what they saw that changed the way economists think about what they see. In this episode of More or Less, presenter-turned-guest Tim Harford explains how. (Image: Mariel boat lift, which brought over 100,000 Cubans into the United States: Photo by Tim Chapman/Miami Herald)