Mothers of the world, if you think you’re missing out on wages because you have children, you are most certainly on to something. A recent study showed that children account for not just some, but most of the gender pay gap.

In a paper titled “Children and Gender Inequality: Evidence from Denmark”—released in February 2017—researchers Henrik Jacobsen Kleven and Camille Landais of the London School of Economics and Jakob Egholt Søgaard of the University of Copenhagen present their findings. As the title implies, this was a study conducted in Denmark, but the researchers note substantial gender inequality “persists in all countries” even with “considerable gender convergence over time.”

The researchers found the arrival of children eventually creates a gender pay gap of about 20%—based on labor force participation, hours of work, and wage rates. Damningly, they call these lost wages “child penalties” and say these penalties relate to an employee’s occupation, sector, and career trajectory, as well as the family-friendliness of their employer for men relative to women.

“This does not rule out discrimination,” the researchers say, “but implies that potential discrimination operates through the impacts of children.”

In one startling statistic, the researchers found that after welcoming a first child, women start becoming less likely to be promoted to manager than their male peers and often switch jobs to work for a more family-friendly company.

With these factors in play, child penalties account for twice as much of the gender gap as it did in 1980, they determined. Back then, child penalties accounted for around 40% of the gap. In 2013, however, they accounted for around 80%.

So why do these penalties persist, even with all the “converging” progress we’ve made? The researchers admit those answers lie beyond the scope of this study, but they speculate it’s an intergenerational problem. “In traditional families where the mother works very little compared to the father,” they write, “their daughter incurs a larger child penalty when she eventually becomes a mother herself.”

All the more reason to show future generations positive examples of work-life compatibility, especially because children are paying more attention than you might think. But the onus shouldn’t be on the mothers. We’ve covered the gender pay gap many, many times here at WerkLife, and each time, it boils down to employers making their workplaces flexible enough to allow women to start families while pursuing their career ambitions—particularly because American women are having more children these days. This kind of workplace flexibility may sound like a daunting challenge for employers, but we have six ways of making it happen.