We propose and implement a new approach to studying the gender gap in wages and how it has changed over time. This approach differentiates between four groups: men who share positions in a multidimensional inequality space with women, women who share positions with men, men in gender-specific (segregated) positions, and women in gender-specific positions. Shared and segregated positions are defined by demographic attributes (e.g., race, education, marital status) and by the job situation (e.g., occupation, industry, work hours, sector). Using data from the 1983-2014 Current Population Survey, we show that the majority of men and women in the United States still work in gender-specific positions, and that even among those who work in shared positions, gender differences in mean wages are substantial and have changed only modestly over the past 30 years. The observed decline in the overall gender wage gap in the 1980s and 1990s was instead driven primarily by wage polarization between men in shared and segregated positions, partially offset by wage polarization between women in shared and segregated positions. We also show that the relative shares of each of the four groups are more unequal in the bottom and top thirds of the wage distribution than at the median, and that change in representation has also been more dramatic at these extremes.