WHILE America’s unemployment rate, at below 4%, is the lowest it has been since 2000, there are many Americans who have exited the workforce altogether. About 37% of the working age population is neither employed nor looking for work. That includes a lot of women who leave jobs when they become mothers and do not return to the workforce for a decade or more. These women account for most of the overall 12-point gap between male and female labour-force participation in America. A new paper by Ilyana Kuziemko, an economist from Princeton, and her colleagues suggests one reason why this “mommy effect” persists even while men and women who aren’t parents now see comparatively equal labour-force participation. It may be getting harder for women to satisfactorily combine work and motherhood.

American mothers born in the years around 1967 are 26% less likely to be working than they were before they had children, with little recovery in the ten years after birth. While that is a smaller “mommy effect” than for previous generations, it is still a considerable drop. And women are not going back to work after becoming mothers even though they thought that they would. In 1978, only 10% of female high school seniors said they would be home-makers at the age of thirty. The actual proportion was twice as high. Since 1990, and despite slightly over-predicting the likelihood they will be mothers, less than 2% of female high school graduates have said they would be home makers by the age of thirty. The actual number is above 15%.

Ms Kuziemko and colleagues suggest one reason behind this unexpected exit from the labour force: women find parenthood more demanding than they thought they would. Indeed, 52% of mothers with children under the age of six report that having a child is harder than they expected; the proportion is higher amongst more educated women. And 66% of current mothers report being a mother is harder today than it was when they were children.

The mothers who try to combine work and child-rearing are often left unsatisfied by the experience. Ipshita Pal, a sociologist at St John’s University has found that while both being employed and being a parent are associated with a higher likelihood that women report themselves to be satisfied with life overall, women who are both parents and employed report lower life satisfaction than those who are either only employed or only a parent.

Changing expectations may help account for these results. After a period where technological advances including washing machines and dishwashers reduced domestic burdens on the women who performed the considerable majority of household chores, evolving norms and new commitments have eroded some of those gains. In 1965, only 20% of American mothers reported ever having breast-fed. Breastfeeding rates were about 50% in 1990 and are now above 80%. In 1994, mothers aged between 25 and 34 spent about 11 hours a week on child-care activities; by the early 2000s that had climbed to 16 hours amongst less educated women and had above 20 hours for more educated women. Debates about “helicopter parenting”—close involvement in children’s lives and decision making—echo across patenting websites, suggesting many mothers and fathers feel trapped by expectations.

Of course, the burden of these expectations is made much heavier by a bigger problem: America’s lack of support for new parents and child care. America has no mandated paid family leave and spends 0.4% of GDP on early childhood care and education—even as the cost of child care has increased about 65% in real terms since the early 1980s. Compare Denmark, where mothers still suffer a considerable drop in earnings after becoming a parent, but they are only 12% less likely to be working. The country spends five times as much on early childhood care and education and mandates 50 weeks of paid parental leave. Given that Americans increasingly expect helicopter parenting, they may have to pay more for helicopter maintenance and support.