100 Women: How US mothers are the new breadwinners

Seventy years ago Rosie the Riveter bared her impressive biceps and summoned American women into the workforce. Called to duty in the service of a country at war, women responded in the millions.

In the decades that followed, women's professional fortunes rose. Today they are chief executives and senators, doctors and lawyers, astronauts and engineers. They are also earners.

Almost half of all American women (40%) with children under the age of 18 are the primary or sole source of income in their families, according to a major Pew survey released this year. Back in 1960, the share was just 11%. It is a huge social shift.

Once, American mothers were dubbed "soccer moms". Then, after 9/11, we got to know the "security moms". Today's generation are the "breadwinner moms".

Rosie the Riveter became a symbol of the US working woman. How are her successors doing?

But to lump all these millions of women together is simplistic. This story of financial revolution is really two stories.

The majority of these breadwinners are single mothers. They have no choice but to be the primary earner in their families, for the simple reason that they are sole breadwinner.

They are the women like Aretha Lewis, who I met in Richmond, Virginia.

She is a dynamo of a woman with four children and as many jobs. She runs her own in-home nursing business, volunteers, has a couple of other jobs on the side and is somehow squeezing in time to start a reality TV show about single mums.

Like many single mothers, she falls in the lower end of the socio-economic scale.

The number of single mothers has grown in America over the past 50 years. That fact we knew. What is really new in this story is that it has been matched by growth in the number of married women who earn more than their husbands.

Back in 1960 those women were a tiny proportion of the working population - just 3.5%. And the number who admitted to earning more was probably a lot less than that.

Today, according to Pew, 22% of married women with kids out-earn their husbands. And as women continue to be better-educated than men, that number is only expected to grow.

What it means for families is dramatic. When a wife starts earning more that her spouse, her work commitments and schedule start to take priority.

Janet and John may both have a heavy work load, but when Janet's salary is $100,000 (£62,500) and John's is $70,000 it becomes more important that Janet can go on that business trip, work late or fill in at weekend.

What does that do to John? Suddenly it means he has to pick up more of the home duties. Women's ability to earn more has a direct impact on the relative involvement of dads - and not in a bad way.

This is anecdotal, but I know several women who earn more than their husbands and even today they don't like to advertise it very much.

Some legacy of tradition still means "real men" are expected to earn more than real wives. The machismo of the pay packet has not disappeared.

But among those couples something has shifted, often something unspoken and barely acknowledged. The husbands are making way for their wives' lucrative careers.

They are the husbands I know who pack more lunch boxes, who have the teacher's number on speed-dial and who have learned what time the dry cleaner closes.

Have women made the gains we thought they would back when they first stormed the corporate barricades? No, possibly not.

We are still paid less on the dollar than men, there are not enough of us in the top ranks of business or politics and we still carry the burden of doing more housework and childcare than our husbands. But I believe that is changing.

As women earn more, we change things not just at home, but in business too.

Women now control 83% of consumer purchases in the US. We've even broken through the car barrier, buying as many cars as men.

The power of our purse is attractive to companies. But there's a catch: women like to buy from people who understand their needs - we like to buy from other women.

At the Ford showroom in Fairfax, Virginia, I found out what that meant in practice. There are more women in senior positions throughout the company, from the boardroom to the sales room.

It's a virtuous circle - when women earn more we spend more, and in response companies employ, retain and promote more of us.

Of course, things are not perfect. But the growing economic power of American women is undeniable and it is changing everything, from politics, to businesses and even families.