The wage penalty for motherhood: Evidence on discrimination from panel data and a survey experiment for Switzerland

Background: Survey-based research finds a sizeable unexplained wage gap between mothers and nonmothers in affluent countries. The source of this wage gap is unclear: It can stem either from the unobserved effects of motherhood on productivity or from employer discrimination against mothers. Objective: This paper opens the black box of the motherhood wage gap by directly measuring discrimination in Switzerland based on two complementary methods. Methods: We first use two longitudinal population surveys to establish the size of the wage residual for motherhood. We then run a factorial survey experiment among HR managers (N=714) whom we asked to assign a starting wage to the résumés of fictitious job candidates. Results: The population surveys show an unexplained wage penalty per child of 4% to 8%. The factorial survey experiment shows that recruiters assign wages to mothers that are 2% to 3% below those of nonmothers. The wage penalty is larger for younger mothers, 6% for ages 40 and less, but disappears for older mothers or mothers in a blue-collar occupation. Conclusions: The motherhood wage gap found in panel studies cannot be reduced to unobserved dimensions of work productivity. The experimental evidence shows that recruiters discriminate against mothers. Contribution: Our paper’s novelty is to uncover wage discrimination against mothers by combining two different methods. Our national panel surveys mirror the supply side of the labor market and provide us with strong external validity. The factorial survey experiment on recruiters informs on the demand side of the labor market and shows a causal effect.