A host of factors have been cited in efforts to explain union decline in the U.S. and elsewhere. Principal suspects in this “whodunnit” have included structural changes in the economy, changes in worker attitudes or values, government provision of benefits once obtained largely from unions, internal union problems, and union suppression and union substitution by employers (Fiorito and Maranto, 1987; Lipset and Katchanovski, 2001). All of these suspects have probably played at least some role in union decline, although there is often substantial disagreement about their relative importance.