Study says moms are the primary earners in 4 out of 10 households

Mothers are the primary breadwinners in four out of 10 U.S. households with minor children, a record number driven up by growing populations of single moms and married women who make more than their husbands, according to a report released Wednesday from the Pew Research Center.

The 40 percent figure is up from 11 percent in 1960, when fewer women worked regardless of whether they had children.

Today, a quarter of the country's households with children under 18 are headed by single, bread-winning mothers, up from 7 percent in 1960. Working moms of kids under 18 out-earn their husbands in 15 percent of households, up from just 3.5 percent in 1960.