They're in charge of the money. Flickr / Rupert Ganzer In 2013, 40% of households with children under the age of 18 were headed by breadwinning women.

That's four times higher than the number of breadwinning women who headed their households in 1960.

Along with earning more, women are also taking control of their family's finances.

According to Farnoosh Torabi, author of "When She Makes More: 10 Rules for Breadwinning Women," women who earn more than their husbands are more likely to make the financial decisions for their household.

Torabi cites studies showing that "in households where the husband earns more money, both spouses share in the financial decision making. But in marriages where the wife brings home a bigger paycheck, the woman is twice as likely as her husband to make all the financial decisions."

The author conducted her own study, and found that it confirmed this trend. Torabi asked over 1,000 heterosexual women in committed relationships if they or their husband managed the household finances. A little more than half of the participants make more than their husbands.

The chart below shows the findings of Torabi's study.

The column on left lists the financial chore, the middle column lists the percentage of non-breadwinning women in charge of that chore for their household, and the column on the right lists the percentage of breadwinning women in charge of that chore.

In every category, from paying household bills to managing the family's investments, women who are the primary income earners are more likely to take on the chore than women who aren't.