Using data on U.S. state-level unionization from Hirsch et al. (2001) and the club convergence test developed by Phillips and Sul (2007, 2009), this paper shows that U.S. states have distinct groupings in terms of the level of unionization. In particular, the states in the American South generally belong to their own low union density groups. Further, states in the Northeast (such as New York) and the Great Lakes regions (Michigan, Ohio) tend to have higher levels of unionization and form their own convergence clubs.
Review of Regional Studies