The Effects of Motherhood Timing on Career Path

This paper estimates the causal effects of motherhood timing on female career path, using national panel data from the NLSY79 and biological fertility shocks to instrument for the age at which a woman bears her first child. Motherhood delay leads to a substantial increase in earnings of 9 percent per year of delay, a smaller increase in wage rates of 3 percent, and an increase in hours worked of 6 percent. Supporting a human capital story, the postponement premium is largest for college-educated women and those in professional and managerial occupations. Family leave laws do not significantly influence the premium. Panel estimation reveals evidence of both fixed wage penalties and lower returns to experience for mothers: a “mommy track ” is the likely channel for the timing effect