In 2011, the median family income was almost $80,000 for couples in which a wife is the primary breadwinner. That's about $2,000 more than it was for couples in which a husband is the primary breadwinner, and $10,000 more than for couples in which spouses' income is the same, the report states.
"This happens because in these types of families they are more likely to have two working parents than the other type of families," said Wang.
The financial picture is very different for the 8.6 million single mothers in the country, as opposed to the 5.1 million married mothers who have a higher income than their husbands.
The median income for families with single mothers is $23,000. The national median income is $57,100 for all families with children.
The percentage of single mothers who have never married has also increased significantly since 1960. Back then, the vast majority of single mothers then were women who were previously married. The percentage of single mothers then who never married was only 4 percent. Now, that figure has increased to 44 percent.