Measuring the effect of the timing of first birth on wages

I study the effect of first-birth timing on women’s wages, defining timing in terms of labor force entry, rather than age. Considering the mechanisms by which timing may affect wages, each is a function of experience rather than age. This transformation also highlights the distinction between a first birth after labor market entry versus before. I show that estimates based on age understate the return to delay for women who remain childless at labor market entry and have obscured the negative return to delay—to a first birth after labor market entry rather than before—for all but college graduates. My results suggest, however, that these returns to first-birth timing may hold only for non-Hispanic white women.