Returns to Seniority in Union and Nonunion Jobs: A New Look at the Evidence

One of the most prominent features of U.S. unionism is the key role played by seniority. However, in cross-sectional data, the positive association between seniority and earnings is typically much stronger for nonunion workers than for union workers. This finding has puzzled previous researchers, since it seems inconsistent with the generalization that seniority is more important in the union sector than in the nonunion sector. We show that standard estimates of the return to seniority are likely to be biased upward and argue that the bias is likely to be larger in the nonunion sector than in the union sector. Corrected estimates imply that the return to seniority is, in fact, larger in the union sector than in the nonunion sector.