Mothers are more likely than fathers or childless people to leave jobs that require long hours - unless the occupations are female-dominated, according to sociologists.

More than one-third of men and nearly one-fifth of women work more than 50 hours a week. Mothers are far fewer than fathers in those numbers. What explains that? Are male-dominated jobs harder on mothers or do some occupations become female-dominated because they are more conducive to women with kids? Does that explain the difference in income?   Male-dominated engineering pays women in America better than any other field while heavily female occupations such as environmentalism and social work pay women far worse than men.

The U.S. White House, which supports laws mandating equal pay, is wildly unequal in pay; 70% of the highest paid staffers are men and men are far more than women on average. The White House staff works incredibly long hours.

A paper in Gender&Society looks for answers, saying 'overwork' contributes to occupational segregation and stalled efforts to narrow the gender gap in white-collar workplaces. Many of the mothers who leave these jobs exit the job market entirely because of the lack of suitable part-time positions in these fields. 

The paper reached its conclusions by analyzing results of the Survey of Income and Program Participation national longitudinal household survey conducted by the U.S. Census Bureau. It included 382 occupations, 173 of which were considered male-dominated, where men made up 70 percent or more of the workforce.  

"Mothers were 52 percent more likely than other women to leave their jobs if they were working a 50-hour week or more, but only in occupations dominated by men," said Youngjoo Cha, assistant professor in the Department of Sociology at IU Bloomington. "Many of these are lucrative fields, such as law, medicine, finance and engineering." 

Cha said workplaces dominated by men tend to operate on outdated assumptions about "separate spheres" marriage -- families with a homemaking woman and a breadwinning man. Yet today, both partners are employed in nearly 80 percent of American couples.

Which means the most lucrative fields allow only one parent to work, and that is more often men. But is it occupational segregation? The word 'segregation' has emotional connotations, a sociologist does not use it by accident.

If gender fairness is the issue, the problem would not seem to be that women are driven out of some fields but rather that men are expected to work long hours. In male-dominated occupations, overwork was more likely than in balanced fields or female-dominated fields.

Yet the sociologist, Youngjoo Cha of Indiana University, Bloomington, seems to know the inner thoughts of working mothers just by using census data on employment, writing in their statement that "mothers in male-dominated occupations were more discouraged despite the fact that the women who survived in those more masculine fields may on average be more committed to work than overworking women in other jobs."

How could a sociologist look at census data and know that mothers are not only discouraged, but discouraged but also more committed than other women in other fields? 

Women with higher education were more likely to stay in their jobs, but Cha still says that is "not enough to overcome the discouraging effect of being an overworking mother". Meanwhile, men (whether fathers or not) and women without children were not more likely to leave their jobs in overworking fields. When mothers left their jobs, some moved to less male-dominated professions while others left the labor force.

Cha advocates labor policies that can reduce work-family conflicts and benefit women, men, families and firms. In her article, she recommends promoting workplace policies that minimize the expectation for overwork, such as setting the maximum allowable work hours, prohibiting compulsory overtime, expanding the coverage of the Fair Labor Standards Act's overtime provisions, and granting employees the right to work part-time hours without losing benefits.

In other words, Cha advocates that getting more mothers working would be worth having fewer part-time people. The moment businesses are forced to pay health insurance for part-time people, or have an hourly cap for a salaried employee, they cease to hire both.