The solid line is the average wage of Black workers as a share of the average wage of White workers. It rose through the 1970s and 1980s, peaked above 80 percent in the mid-1990s, and has drifted back into the low 70s since.
The dashed line is the average wage of female workers as a share of male workers. It barely moved through the 1970s, then climbed steadily from the early 1980s onward, and by the 2010s had passed the Black to White ratio. In both cases a substantial gap remains. A gap between average wages is not by itself proof of discrimination, since it does not hold constant education, experience or occupation, but it is where the analysis starts. The slider reads both series at a chosen year. The values are sampled from the book's figure, so they trace its lines rather than the published series.