WATERTOWN, Mass. (BUSINESS WIRE) — A new study released Dec. 20 shows that even as women catch up to men as family earners and actually outpace them in academic achievement, they continue to bear a disproportionate portion of household and family responsibilities.

According to the study, women who are primary breadwinners are doing more at home than their male counterparts and even more than working mothers who are not providing their family’s primary financial support. Mothers with jobs that provide their family’s major source of income are also two and three times more likely to be managing the household and children’s schedules than breadwinning fathers, and more than 30 percent more likely than other working mothers to be taking care of everything from family finances to organizing family vacations.

The fourth annual report in the Modern Family Index (MFI) series, commissioned by Bright Horizons Family Solutions (NYSE:BFAM), shows that the concept popularly known as “mental load” is real and measurable. More than just responsible for their half of the parenting and household duties, working mothers are also organizing, reminding and planning virtually all family matters.

Surprisingly, the household responsibilities only increase when these women are bringing home the primary paycheck.

While 40 percent of today’s families have female breadwinners:

• Breadwinning mothers are three times more likely than breadwinning fathers to be keepers of their children’s schedules and responsible for them getting to activities and appointments (76% vs. 22%)
• They’re three times more likely to volunteer at school (63% vs. 19%)
• They’re nearly twice as likely to make sure all family responsibilities are handled (71% vs. 38%).

While much anecdotal evidence about mental load exists, the 2017 MFI offers some of the first concrete data showing the effects on women are real.

In an era where women and men may be working side-by-side as nearly equal parts of the workforce, workplace cultures continue to favor men as employees and women as mothers, unintentionally keeping the household responsibilities squarely in the women’s camp — even as they carry a full professional load.

Despite the fact that 75 percent of mothers with children under 18 are employed full-time:

• 86 percent of working moms say they handle all family and household responsibilities
• 72 percent feel it’s their job to stay on top of kids’ schedules
• 63 percent have missed work to take care of their sick children.

More work at the office means more responsibility at home, too, with female primary earners taking on even more household jobs than other working mothers. Primary breadwinning women are:

• 34 percent more likely than other working mothers to manage the family finances (71% vs. 53%)
• 63 percent more likely than other working mothers to maintain the yard (31% vs. 19%)
• 30 percent more likely than other working mothers to organize family gatherings and vacations (73% vs. 56%)
• 38 percent more likely than other working mothers to take care of home maintenance (33% vs. 24%)

With so much on their plates, it’s not surprising to learn that working mothers are carrying much of this mental load into work. Women are committed to their jobs and eager to grow professionally — last year’s MFI showed that more than half of new moms are personally fulfilled by their job.

But a large number of this year’s respondents say the mental load, and not just time commitments, requires them to work much harder to fulfill all their responsibilities:

• 69 percent of working moms say their responsibilities create a mental load.
• 52 percent are burning out from the weight of their household responsibilities.