Women returning to work part-time after the birth of their children are being hit by a “pay penalty”, a new study has found. 

The research, conducted by the Institute for Fiscal Studies (IFS) for the Joseph Rowntree Foundation, found that by the time a child is 20, mothers are earning on average a third less per hour than fathers with similar experience and educational background.

Part-time work often fails to reward employees with the same job progression or pay increases that full-time employment provides – meaning that women are not experiencing the same level of wage progression as their male colleagues. “The effect of part-time work in shutting down wage progression is especially striking,” the report explains.  “Whereas, in general, people in paid work see their pay rise year on year as they gain more experience, our new research shows that part-time workers miss out on these gains.”

Most of those occupying part-time roles are women – and associate director of the IFS Monica Costa Dias said that it was “remarkable” that periods in part-time work “lead to virtually no wage progression at all”. 

The report suggests several factors that might explain the reason behind the lack of wage progression in part-time roles: fewer training opportunities, missing out on “informal interactions and networking opportunities” and “genuine constraints placed upon the build-up of skill by working fewer hours”.

One of the reasons so many women are in part-time work, the report also explains, is because of the cultural expectations placed upon women to take increased responsibility for childcare. Men’s rates of part-time employment, for example, are largely unchanged by the arrival of a child – something that isn’t the case for women.

This also explains the report’s findings that the pay gap widens dramatically during employees’ late 20s and early 30s – because women are largely tasked with looking after children during these years. 

The gap isn’t just because of motherhood, however: the report also found that even before giving birth, women were being paid around 10% less than men. “This gap is fairly stable until the child arrives and is small relative to what follows,” the report explains. “There is then a gradual but continual rise in the wage gap and, by the time the first child is aged 20, women’s hourly wages are about a third below men’s.”

The study also found that the gender pay gap has “not improved since 1993” for graduates  – though the gap has narrowed for non-graduates. 

This means that lack of wage progression is a particular issue for graduate women, as they are the women for whom “continuing in full-time paid work would have led to the most wage progression” – as in the case of a graduate featured in the report who worked for nearly ten years before having her first child. If she’d continued in full-time work for an extra year, she would have “on average see[n] her hourly wage rise by 6%” – something she’d experience “none of” if she switched to part-time work to look after her child. 

“Traditionally it has been lower-educated women whose wages were especially low relative to similarly educated men,” said Robert Joyce, associate director at the IFS and co-author of the report.  “It is now the highest-educated women whose wages are the furthest behind their male counterparts - and this is particularly related to the fact that they lose out so badly from working part-time.”

Businesses with more than 250 employees have been set a deadline to report their gender pay gaps by 4th of April as part of a governmental plan to tackle pay inequality. 

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