Mothers working in France are paid 3% less for every child they have compared to their female colleagues who do not have children according to new research from Université Paris-Saclay.

The research also shows that fathers suffer no such pay penalty at all.

For the data, Lionel Wilner, Director of Graduate Studies at engineering and statistics school ENSAE and founding member of the Université Paris-Saclay, studied 16 years of data from organisations in the French private sector between 1995 and 2011.

Wilner separated the effect of childbirth from other firm-specific wage determinants, and accounted for full-time and part-time work, to find that the difference between mothers and non-mothers is approximated a 3% lower hourly wage. The effect was found to be more pronounced after the birth of the first child.

“The gender pay gap, occupational gender segregation and the glass ceiling are the most striking examples of gender inequality – but an obvious example is related to childbirth,” Wilner said.  “The motherhood penalty accounts for noticeable hourly wage differences following childbirth.”

Wilner finds that human capital depreciation is to blame, alongside discrimination against mothers at work. Mothers can be allocated a role with less risky assignments, so are less likely to receive bonuses or more likely to become trapped in low-wage trajectories. Men do not experience any loss after childbirth, but do not enjoy any benefit suggested by previous research.

“This is both unfair and inefficient. It requires further public intervention, including campaigns against discrimination, development of on-the-job childcare, and extension of paternity leave,” Wilner said. “A paternity leave of the same duration as maternity leave would bring down this gender gap.”

Kate Headley, Director of HR and diversity consultancy, the Clear Company, also commented, “Wilner’s research confirms what many commentators have long suspected – that rifts in the gender pay gap can be directly related to motherhood. Organisations need to create an inclusive culture to which equality and diversity are fundamental if they truly want to address gender inequality in the workplace. A reliance on targets or quotas to improve diversity and inclusion without a focus on fostering cultural change, will only perpetuate this issue, and risks putting mothers at an even greater disadvantage.”