The study reflects social norms that may be partly responsible in lowering women’s pay, said Bertrand, who is married and has two children, ages 3 and 6. In a separate report published in May, she and her co-authors found that couples have an aversion to a wife earning more than a husband -- so much so that when the wife’s salary approaches her husband’s, it can result in reducing her labor-force participation and marriage satisfaction and creates a higher likelihood of divorce.

Surveys suggest most women can’t “have it all,” Bertrand said. College-educated women with careers spent a larger share of their days “unhappy, sad or stressed and tired” compared with mothers who stayed home, according to data she has studied.

Stressed, Frustrated

Bertrand says “there is no doubt” she is sometimes “stressed and frustrated” balancing her career and family, even though she’s had a nanny for the past six years.

“I have two kids, so I do lots of kids’ stuff; I watch kids’ movies,” she said. “The only thing I have tried to keep on doing, but that has been kind of crushed, is cooking because that is something I really like.”

She says she spends two days a week in class, two days with research and a day editing an economic journal during the quarters when she teaches. “A smaller and smaller part of my time is spent is research, unfortunately.”

While Bertrand says she’s never faced gender discrimination, she sees its effect in her classroom: Females participate less. In a recent elective course -- “The Firm and the Non-Market Environment” on how companies confront outside forces such as regulation, the press and interest groups -- Bertrand went over cases involving BP Plc and Royal Dutch Shell Plc. She tossed out questions on their crisis management and studiously avoided showing how she felt.

Speak Up

During a 15-minute break in one class, she urged two Chinese women, who hadn’t contributed to the discussion, to speak up in the second half. More than 30 percent of her students are women and about the same proportion are foreign.

“Non-Americans, especially in Asia, just don’t talk that much in class -- it is just not the norm,” she said. That reluctance could hamper careers and pay. “You can imagine some workplace where they are just going to have to be more vocal” or speak up to ask for a promotion.