Abstract
Relying on the data of the Swiss Household Panel, the paper aims to make sense of the puzzling dissatisfaction union members exhibit in most dimensions of their job. A longitudinal approach reveals that the dissatisfaction is to a large extent explained by contextual and individual time-invariant unobserved heterogeneity. A decline in job satisfaction is for many workers the main reason to join a union. Job satisfaction climbs back as the years of membership increase, which confirms that unions do indeed have positive effects on the professional well-being of their members.