Winning is Contagious: Social Learning and the Dynamics of Union Support

Union growth has historically happened in spurts. We combine union election data from 1961–2025 with a large-scale information experiment involving 9,000 low-wage workers to study the role of social learning in union growth. Observationally, close election wins cause future wins within state-industries. Experimentally, information about recent union wins increases union support and beliefs about co-worker support, with effects concentrated among workers with weak information environments and low baseline coworker support. In contrast, information about labor market tightness has little effect. Our results highlight social learning as a mechanism for union growth.