Moms get interrupted a lot more than dads. And the price is steep.

Other moms, long used to getting asked about kid-related stuff, might have taken the requests in stride. Or griped. Or whatever.

But Gee — an economics professor at Tufts — turned to her fellow economist moms. “We all just started to complain to each other about this phenomenon,” Gee says. Which is when they decided to understand the scope of the problem.

Turns out, it’s enormous, and the implications for women’s careers — and for fathers who want to take on more of a role in parenting — are profound.

In their experiment, Gee — along with Kristy Buzard of Syracuse University and Olga Stoddard of Brigham Young University — sent out more than 80,000 emails to school principals. The emails originated from a fictitious mom and dad “searching for a school for their child.”

The mom and dad always signed the email with both of their names and provided both of their phone numbers. Sometimes the mom signed the email first; sometimes the dad signed first. And they asked the principal to give one of the parents a call.

Not surprisingly, perhaps, moms got most of the calls — about 60 percent. And Gee believes the gap may have been even larger if the calls had come from doctors’ offices or dance classes — places where women tend to play an even more outsized organizational role for their kids.

Sometimes, the researchers sent out a variation of the email noting that the father was actually the more available parent. But, in that scenario, more than a quarter of calls still went to mothers.

The study found that the preference for contacting moms was greater in religious schools and more Republican-leaning areas. But, Gee points out, no one was immune from preferencing moms. “Even in Somerville, there is inequality,” she told me with a smile.

And the impacts of getting called all the time — by school, by the dentist, by gymnastics class — add up over the course of a career. In a related survey conducted by Gee and her colleagues, most women — but fewer than a third of men — reported that they took these sorts of interruptions into account when looking for a job. Women sought jobs with more flexibility and a shorter commute. And many admitted that “child-related interruptions” had either caused them to choose a job with lower pay or had resulted in lower pay.

Women know what society expects of them, and they often conform to those expectations (as Gee’s paper notes, women make up nearly 90 percent of PTA members).

So what happens when women choose more flexible jobs, allowing them to accommodate unexpected illnesses or extracurricular activities? As Harvard’s Nobel Prize-winning economist Claudia Goldin has argued, they frequently have to make financial sacrifices.

Many of the most lucrative jobs are what Goldin has called “greedy jobs.” Think consultants, executives, partners in a law firm. These sorts of jobs are hungry for your time, perhaps requiring a last-minute trip or a few hours of work on a Saturday night. They are inflexible and demanding.

But, of course, having kids is also demanding. There will be days when a parent will have to drop everything to care for a kid with strep throat. There will be days when a child has to be chauffeured to a 9 a.m. dentist appointment, then dropped off at school afterward.

Couples made up of two college graduates, Goldin has written, are frequently “faced with a choice between a marriage of equals and a marriage with more money.” And, in marriages of a man and a woman, it is often the man who takes the lucrative job, while the woman opts for the job that accommodates the inevitable family-based interruptions.

Gee and her colleagues note that mothers report household-related interruptions 75 percent more often than fathers. And that, they argue, “come[s] at a significant economic cost to women, stunting labor market outcomes, human capital accumulation, and economic growth.” Every hour of interruption correlates with a 3.4 percent decline in wages for women, they find.

Princeton professor Henrik Kleven has argued that the “motherhood penalty” in the United States is considerable. Before having children, women and men earn similar amounts. After a woman has her first child, though, her earnings drop by more than 30 percent, on average. Ten years later, her earnings have still not recovered. (Men’s earnings do not go down when they have their first child; some research has shown they actually increase.)

This is considerably worse than in Denmark — where women see a 21 percent drop in income after their first child — but quite a bit better than in Germany, where women experience a 61 percent drop, according to Kleven and his colleagues. Women’s reduced earnings come from a combination of a reduction in hours and a lower rate of compensation.

Still, in a world with plenty of female surgeons, financial executives, and high-powered lawyers, aren’t there women who are simply unavailable to take a call from their child’s school? Or to do a last-minute pick-up?

Yes, says Gee. But those women are still being disproportionately interrupted. And they have to figure out how to redirect (or otherwise deal with) incoming calls. Dads, by contrast, are often never interrupted in the first place.

Increasingly, though, dads want to be contacted. Over the last 30 years, there has been a sharp increase in the number of men with primary parenting responsibilities, according to the Pew Research Center. Dads now make up 18 percent of stay-at-home parents, up from 11 percent in 1989. Gee says she hears from dads who “want to be involved too, and they’re feeling left out.”

When Gee and her colleagues polled parents, they found that “women report being contacted by the school more often than men, yet wish they were contacted less often, while men wish they were contacted more often.”

So how do we rebalance parenting responsibilities? Gee would like to see structural changes.

Take schools. They often request both parents’ contact info but also want a primary contact. For many people, that’s impractical. “That means that one person has to decide,” Gee says. “For the rest of this child’s life in school, every day of the week, I get to be the first line of defense.”

What if schools instead allowed you to designate different primary contacts on different days? Or randomized which parent’s contact info popped up on the computer (assuming the parents had requested equal treatment)?

Right now, society expects that mom is always on the case — even when she really needs to get some work done. And the consequences of those expectations ripple outward, altering career trajectories, paychecks, and possibilities.

Follow Kara Miller @karaemiller.