‘‘I’m sorry to say this, but if you think that, you’re wrong,’’ she wrote to high-schoolers Monday in her annual open letter, penned with her husband, Bill Gates. ‘‘Unless things change, girls today will spend hundreds of thousands more hours than boys doing unpaid work simply because society assumes it’s their responsibility.’’
She backed her case with global data. Women worldwide devote an average of 4.5 hours each day to unpaid work — cooking, cleaning, changing the baby’s diaper. Men contribute less than half that much time, according to the OECD.
The domestic division of labor remains staggeringly unbalanced in the United States, where female breadwinners now support 40 percent of homes. Women here typically spend two hours and 12 minutes daily on housework, while men spend one hour and 21 minutes.
A 2015 survey by Working Mom, furthermore, found that female breadwinners who lived with male partners still reported handling the bulk of the grocery shopping, meal preparation, bill-paying, and cleaning.
‘‘This isn’t a global plot by men to oppress women,’’ Melinda Gates wrote. ‘‘It’s more subtle than that. The division of work depends on cultural norms, and we call them norms because they seem normal — so normal that many of us don’t notice the assumptions we’re making. But your generation can notice them — and keep pointing them out until the world pays attention.’’
(Bill Gates, it should be noted, drives their kids to school every other day.)
Mothers in the United States who work full time, year round, make an average of $40,000, compared to $56,999 paid to fathers, according to the National Women’s Law Center. That’s 70 cents to the dollar.
Economists say this disparity probably comes from a blend of factors: Women are sometimes ‘‘mommy tracked,’’ or passed over for high-profile projects or promotions, when employers assume motherhood (but not fatherhood) zaps productivity. A 2015 study from the University of Georgia found that, for this reason, expectant mothers are often afraid to tell their bosses they’re pregnant.
Women do take more time off to tend to family, but that’s not always a choice. Sometimes, as the data show, husbands just don’t pull their domestic weight. They also tend to prioritize their careers over their wives’, while wives tend to equally prioritize both partners’ careers, according to a 2014 study of 25,000 Harvard Business School graduates.
Evidence for the wife (or husband) penalty shows up in what researchers call the ‘‘lesbian wage premium.’’ Across years of research, women who have never lived with a male partner make more money than women who have.
Last year, Marieka Klawitter, a professor of public policy at the University of Washington, examined 29 studies across the Western Hemisphere on wages and sexual orientation and found a 9 percent earnings premium for lesbians over heterosexual women. Gay men, meanwhile, faced an 11 percent penalty, compared to straight men.
She controlled for parenthood and concluded that lesbians simply had more education and work experience than the general female population.
But another study from the University of Nevada, which used national data from the year 2000, adds a stunning asterisk to Klawitter’s findings: Lesbians who had previously lived with male partners made 20 percent less than those who’d never cohabitated with a husband figure.