Mitt Romney’s wife, Ann, a woman of multimillion-dollar net worth, became a symbol of stay-at-home mothers last week after a flare-up on the campaign trail went viral. But fewer than a quarter of married women who are homemakers with minor children live in households with family income over $100,000, according to census data…

Such mothers are younger, less educated and more likely to be Hispanic than they were in previous generations, and perhaps have a more traditional view of family and more limited job skills than other women these days, according to a Census Bureau report that analyzed changes in stay-at-home motherhood from 1969 to 2009. Eighteen percent of stay-at-home mothers lack a high school degree, compared with 7 percent of women in the work force. And black women were about half as likely as white women to be a stay-at-home mothers.

Across the country, 70 percent of married women over age 25 with children work outside the home. The median income of those households is about $87,700, compared with $64,000 for households where the mother stays at home, according to an analysis by Andrew A. Beveridge, a sociologist at Queens College of the City University of New York. “The biggest difference is education,” he said.