Brightly clad delivery drivers, darting in and out of restaurants and traversing the city on bicycles, mopeds, or in cars, have become a persistent sight across urban areas. Their routines persist even when heavy rain or oppressive heat empties the sidewalks. These delivery drivers are the most visible representatives of a growing segment of the labor market: gig workers, who have no stable employment contract but get paid for each task they complete. The recent rise of gig work has been driven by technological advances, like smartphones and the Internet, which allow for just-in-time coordination. Yet the work arrangement itself is not a novel phenomenon. In early industrial England, handloom workers were typically paid per piece, dockworkers in the nineteenth and early-twentieth centuries were hired on a daily basis, and day laborers have been common in agriculture since ancient times. In fact, from a historical perspective, the formal employment exemplified by unionized work in the post-war era is the aberration. Yet such formal employment has become the norm throughout wealthy countries. Our social safety nets …