Neil Buchanan (GWU) uses U. Mich. Law School alum data in his paper that explores the complex relation between gender and lawyer salaries. His paper reports that:
tend to receive higher salaries than non-fathers (a "daddy bonus"). In
addition, mothers earn less than non-mothers (a "mommy penalty"). There
is also some statistical support for the inference that there is a
penalty associated purely with gender (women earning less than men,
independent of parenthood), another result that is unique to the
Analyzing full- or part-time status as well as work hours also suggests a key difference between women and men. Those who take part-time status are almost entirely women who take on child-rearing duties, and they reduce their work hours by an average of approximately thirty percent. These statistical results are, however, significantly less reliable because of the very small numbers of respondents (male or female) who work less than full time."