Something I find rather interesting is the form of sexist discrimination revealed by the data. It's not so much the case that women are discriminated against as individuals (though this does play a role; see part 3, 'Men get more credit for their work'); rather, there are numerous small, systematic biases that work against women, such as the second shift (men are much less likely to do work around the house than women, regardless of out-of-the-house employment) and the structure of a career (women who try to work part-time the first few years of the lives of their children are often pushed out of employment entirely, and then find it much more difficult to return later).
Discrimination in the workforce is usually is a matter of “cumulative causation.” Among other things, this means that the effects of discrimination add up over a lifetime. So, for example, losing a single job offer or promotion usually won’t make a big difference; but dozens of such small losses over the course of women’s careers eventually add up to a big wage gap.
This is important, because it means we should expect the pay gap between men and women at the start of their careers to be small. The effects of discrimination build up gradually over time, and only becomes sizable once women have been in the job market long enough for the impacts of dozens of individual instances of discrimination to add up.