Family focus or career focus: controlling for infertility.

In order to shed light on the direction of causality between fertility timing and earnings, this paper uses medical diagnoses of infertility as instruments for age at first birth (for those women who did give birth) and childlessness among married women. Although multivariate ordinary least squares regression results find a positive correlation between childbirth at later ages and higher wages as well as between childlessness and increased wages, delays in childbearing due to infertility do not significantly increase a woman's wages. Thus, data from the 1995 National Survey of Family Growth (NSFG) indicate that delaying childbirth does not, by itself, guarantee higher wages in the labor market. Therefore, this study does not support the conventional notion of the 'mommy track' in which career success and motherhood are incompatible.