Gone are the days of stay-at-home moms. Trending now are dads doing housework and changing diapers at home.

Moms are the sole or primary source of income in a record 40 percent of all families with children younger than 18, according to a study by Pew Research Center. That number has almost quadrupled since 1960.

What's more fascinating is: The total family income is higher if the mom, not the dad, is the key breadwinner.

The median family income of married women who out-earn their husbands was nearly $80,000 in 2011, more than $20K over the national median for all families with children, according to Pew Research Center.

Single-mom families, however, are not doing so well, with the median standing at a little more than $20,000.

The “breadwinner moms” in the Pew study are made up of 5.1 million married women who earn more money than their husbands, and 8.6 million single moms.

Besides the above-mentioned income gap, the two groups of women also have apparent dissimilarities in age, race and education.

According to Pew Research Center:

Compared with all mothers with children under age 18, married mothers who out-earn their husbands are slightly older, disproportionally white and college-educated.

Single mothers, by contrast, are younger, more likely to be black or Hispanic, and less likely to have a college degree.

Even though more moms are becoming top breadwinners in the family, almost half of the survey respondents still believe children are better off with mom at home. Only 8 percent say the same about dads — that American kids are better off with Mr. Mom — according to Pew Research Center.

The bottom line is, you've got to do what's best for the children.

When it comes to single moms, most Americans (64 percent) view this trend as a big problem affecting the well-being of children. But the number of people who feel that way has dropped by 7 percent since 2007, according to Pew Research Center.

Looks like the ingrained notions on women's role in a family have been changing. But not so fast.

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