This study examines the gender wage gap, to explore whether a glass ceiling (large unexplained wage gaps in the upper percentiles) or sticky floor (large unexplained wage gaps in the lower percentiles) exists in the wage distribution of the most educated Koreans. This study focuses on seeking these distributional patterns for a theoretically homogeneous gender group, relying on a smaller dataset of PhD holders. Counterfactual methods combining recentered influence function decomposition with propensity score matching allow us to estimate how the wage gap between statistically similarly matched males and females, varies across the unconditional wage distribution. There is evidence of a strong sticky floor and a limited glass ceiling among Korean PhD holders. Results show that a negative relationship between a high level of education and the gender wage gap cannot be taken for granted, at least in South Korea. Even female PhD holders suffer from gender discrimination, especially when they are at the bottom end of the wage distribution.

Whether the dual labor market structure implied by employment type and unionization causes wage discrimination is an intriguing and relevant policy question in the context of South Korea. This study examines the effect of trade unions on wage discrimination against irregular workers by extracting and comparing the ratios of the discriminatory wage gap by employment type between unionized and non‐unionized workplaces. As per the analysis, all generalized decomposition frameworks show that the presence of trade unions expands discrimination regardless of the employment type. In addition, the effects of unionization on the degree of discrimination differ by factors characterized by the dual labor market. The effects are statistically significantly greater for women, youth, service industries, and white‐collar jobs.