With the recession on the brink of becoming the longest in the postwar era, a milestone may be at hand: Women are poised to surpass men on the nation’s payrolls, taking the majority for the first time in American history.

The reason has less to do with gender equality than with where the ax is falling.

The proportion of women who are working has changed very little since the recession started. But a full 82 percent of the job losses have befallen men, who are heavily represented in distressed industries like manufacturing and construction.

Women tend to be employed in areas like education and health care, which are less sensitive to economic ups and downs, and in jobs that allow more time for child care and other domestic work.

“Given how stark and concentrated the job losses are among men, and that women represented a high proportion of the labor force in the beginning of this recession, women are now bearing the burden — or the opportunity, one could say — of being breadwinners,” says Heather Boushey, a senior economist at the Center for American Progress.

A deep and prolonged recession may change not only household budgets and habits, but it may also challenge longstanding gender roles.

In recessions, the percentage of families supported by women tends to rise slightly, and it is expected to do so when this year’s numbers are tallied. As of November, women held 49.1 percent of the nation’s jobs, according to nonfarm payroll data collected by the Bureau of Labor Statistics. By another measure, including farm workers and the self-employed, women constituted 47.1 percent of the work force.

Women may be safer in their jobs but tend to find it harder to support a family. For one thing, they work fewer overall hours than men. Women are much more likely to be in part-time jobs without health insurance or, for that matter, unemployment insurance. Even when working in full-time jobs, women earn only 80 cents for each dollar of their male counterparts’ income, according to the government data.

“A lot of jobs that men have lost in fields like manufacturing were good union jobs with great health care plans,” says Christine Owens, executive director of the National Employment Law Project. “The jobs women have — and are supporting their families with — are not necessarily as good.”