Labor union effects on wage dispersion: Evidence from panel data of Japanese listed companies

We examined whether (1) unions can reduce wage dispersion, (2) their influence has changed over time, and (3) their influence differs depending on firms’ ownership structure. Combining three data sources, we created a panel dataset that included data from 2004 to 2015. Partly since our dataset covers a relatively short period, we found very small changes in union status. Thus, a hybrid model was used to address the data challenges. We found that first, the between-effects results show that labor unions play a role in decreasing wage dispersion. Second, the union effect gradually decreased during the sample period. Third, foreign investors (financial institution shareholders) and labor unions are substitutes (complements) in reducing wage dispersion. We confirmed that (1) and (3) were valid after employing an endogenous treatment effects model to address the endogeneity problem of the union dummy. Thus, unions’ bargaining power depends on differences in the corporate governance structure.