This dissertation consists of three essays studying the occupational wages, skills, and gender wage gap in U.S. and other OECD countries. The analysis especially focuses on how the gender differences in skill levels and skill returns could explain the gender wage gaps and changes. The first chapter outlines the dissertation by briefly discussing the motivations, methods, and main findings in each of the following chapters.

Chapter 2 focuses on the well-documented wage and employment polarizations in the U.S.. The occupations moving into the lower tail ("in" occupations) have more immigrant workers, more part-time workers, and less female workers. In addition, the wage gaps between domestic/immigrant, full-time/part-time, and male/female workers are also larger in "in" occupations. The opposite facts hold true in the occupations moving out of the lower tail ("out" occupations). Utilizing the regional differences, we also find stronger spillover effect from high-wage occupations to the "out" occupations than the effect to the "in" occupations.

Chapter 3 investigates how gender differences in skills beyond education and experience can account for the observed gender wage gap and its changes between 1980 and 2015 by using data from the Dictionary of Occupational Titles (DOT) and the Occupational Information Network (O*NET). The main empirical finding is that female workers possess much higher level of caring skills, and the returns to caring skills are significantly negative but have increased over time, accounting for a major part of the persistent gender wage gap and the narrowing gender wage gap from 1980 to 2015. Another significant portion of the narrowed gender wage gap can be attributed to the faster growth in female workers' average directness skills and the fact that the returns to directness skills are significantly positive and stable over time.

In the last chapter, we document significant cross-country variation in gender wage gaps among OECD countries by using the data from Survey of Adult Skills (PIAAC). We find significant cross-country variation in the gender differences in returns. The gender differences in returns to basic labor and experience are the most important factors in explaining the gender wage gap. In addition, gender differences in returns to cognitive and directness skills are playing milder but substantial roles in explaining the wage gap. We also find the social institutions and attitudes indicators are related to the cross-country variation in gender differences.