Wendy Wang, Kim Parker, and Paul Taylor have produced a study published by the Pew Research Center (May 2013) in which they conclude that 40% of households with children have mothers who are the sole or primary "breadwinner." In comparison, in 1960, this number was only 11%, thus the "Breadwinner Mom" demographic has nearly quadrupled since the end of the Eisenhower years.
Among the contemporary mothers who are the sole or primary breadwinners, 63% are single moms. The other 37% are married women who earn more money than their spouses.
This study provides further evidence that family structure and gender roles are evolving dramatically, an evolution with profound economic consequences.
The study is linked below:
Pew Research Center: 40% of American Households With Children Have Breadwinner Moms