Do women want to work more or more regularly? Evidence from a natural experiment

In France, a four-day school week schedule affected mothers’ professional advancement and contributed to the gender wage gap.


Historically, French primary schools follow a four-day school week with schools being closed on Wednesdays, giving children a day off in the middle of the week. This schedule was replaced by a national reform reallocating weekday classes to Wednesday mornings and introducing three hours of optional daily extracurricular activities. Given that French households continue to display a traditional division of gender roles, this reform had the potential to reshape working mothers’ professional lives by easing childcare responsibilities. Previous research has shown that women’s greater demand for flexible work hours is coupled with the lower wages, contributing to the persistence of the gender wage gap.

As the debate about implementing four-day school weeks spreads globally, this is the first study to assess the French school week reform’s professional impact on mothers. Using French labor force data, this study evaluated whether mothers’ demand for flexible work hours decreased when schools added class time on Wednesdays. Next, the study investigated whether mothers were rewarded for increasing their availability to work longer, more regular hours during the week.


Having children decreases women’s chances of having a regular Monday to Friday workweek, contributing to the persistence of the gender wage gap. To test the impact of France’s reform, “treated mothers,” those whose youngest children were in primary school, were compared with the “control group” of mothers, whose youngest children were in middle school, so they already had class on every weekday.

  • In the pre-reform period, more than 40% of working mothers with primary school children stayed home on Wednesdays, compared to only 35% of those with older children.
  • Treated mothers took advantage of the reform to adopt a regular Monday to Friday workweek.
    • Treated mothers closed 40% of the pre-reform Wednesday-gap with the control group, displaying greater impact over time.
    • Some mothers took advantage of the reform and switched their work hours from Saturdays to Wednesdays.
    • Treated mothers’ probability of working part-time decreased by 5% compared to the pre-reform mean.
    • Overall, treated mothers increased their number of workdays, halving the pre-reform gap with the control group.
  • Treated mothers experienced a 1.5% increase in hourly wages relative to the pre-reform levels, corresponding to a 6% decrease in the pre-reform gender wage gap.
  • The reform’s effects on fulltime work and wages were driven by highly skilled mothers.
    • Highly skilled mothers’ weekly work hours increased by an average of almost one hour.
    • Highly skilled mothers’ wages increased by more than 3%.
    • This effect corresponds to a 10% decrease in the pre-reform gender wage gap.
  • Fathers’ probability of working on Wednesdays did not differ from other weekdays either before or after the reform.

These findings demonstrate that once constraints were relaxed, mothers were more likely to work on Wednesdays and to work full-time. By working longer and more regular hours, mothers were able to reduce the gender wage gap. These results are consistent with the canonical consumption/leisure two-period model with promotion, which shows how mothers’ optimal time allocation responds to the provision of free childcare and explains why highly skilled mothers had a greater labor supply response to the reform. Overall, this study indicates that the four-day school week may hurt mothers’ professional prospects, particularly for highly skilled women.


This study was conducted using a difference-in-differences policy analysis, focusing on a sample of 175,528 French mothers aged 18-55 whose youngest child was 6-14 years old, and 149,794 fathers within the same parameters, excluding those working in schools. This study compared French mothers whose youngest child was primary school age (6-11 years old) with mothers whose youngest child was middle school age (12-14 years old). The data for this study come from the 2009-2016 waves of the French Labor Force Survey, as well as the Enrysco database. The empirical results of this study were shown to be consistent with a simple theoretical framework, the canonical consumption/leisure two-period model with promotion.

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