When I was a single mother in my early 20s, reality was routinely choosing between buying diapers or buying food, and struggling to find sitters to watch my infant son while I tried to get a job that would feed us and keep a roof over our heads — even if it was just the roof of a converted garage. I took some comfort in knowing that I was not alone in this struggle and was one of millions of American women trying to make ends meet.

But I also learnt that in too many industries, women are undervalued and under-compensated.

As my career progressed, I have been able to earn a living doing what I love. And while there’s no question that it’s a privilege for anyone, woman or man, to have that opportunity, it doesn’t mean we can overlook circumstances — whether it’s waiting tables or acting in films — in which men get paid more than women for doing the same jobs.

Yes, it’s about the paycheque. But it’s also about the principle of fairness. That’s what April 12, Equal Pay Day, was about.

Women earn only 79 per cent of what men make in comparable jobs. And the numbers are more striking when you consider that African-American women make only 60 cents and Latinas make only 55 cents compared with white men. A new report out this week, “Gender Pay Inequality: Consequences for Women, Families and the Economy,” commissioned by Carolyn Maloney of New York, the ranking Democrat on Congress’s Joint Economic Committee, shows that women’s median earnings are now $10,800 less per year than men’s.

The disparity adds up to more than a $400,000 gap over a 40-year employment lifetime.

The wage gap has narrowed since the Equal Pay Act first became law in 1963 — when women made only 59 cents on the dollar compared with men — but we have to take a sober look at gender-pay inequality in the America of today. The iconic “Ozzie and Harriet” family of Dad at work and Mum at home with two children is no longer the norm. Three quarters of all working-age women are now holding or seeking a job, including two thirds of women with children under 18, and 40 per cent of employed married women are their household’s prime wage earner.

Because women make less, we will wait longer than men to buy a house, and take longer to pay off student loans. Because job segregation and discrimination can steer women to lower-paying work in general, women are less likely to have health insurance, paid vacations or sick leave.

We live in the only advanced country that does not guarantee paid maternity leave for employed mothers. And bonuses, stock options or “golden parachutes” are often off the table for women, even at the top end of the pay scale.

Employed mothers often face a “mommy penalty”, taking home less than women without children, while many fathers get a “daddy bonus”, making more than men without children — an unmistakable double standard. But it doesn’t have to be this way.

The push for increasing women’s wages started in the 1960s with the Equal Pay Act, individual lawsuits and action by the Equal Employment Opportunity Commission.

The message, then and now, is so powerful that when people hear it they begin to take action.

For example, the California Fair Pay Act, authored by State Senator Hannah-Beth Jackson, a Democrat from Santa Barbara, passed with bipartisan support and gives California women the strongest fair pay protection in the nation.

Recently, Salesforce chairman and chief executive Marc Benioff reviewed his 17,000 employees’ salaries and made $3 million in adjustments to equalise gender pay disparities. A wage discrimination complaint, filed last month by five members of the US women’s football team, who are the world champions, but, according to their claim, make a quarter of what the men’s team do, may shift the spotlight, a little, to unequal pay for men and women athletes.

Whether we’re talking, though, about Lilly Ledbetter being underpaid for her work in a tyre factory, Betty Dukes working in retail, teacher Aileen Rizo, world-class athletes or Hollywood actresses, unequal pay for men and women is harmful fact of American life.

And as I’ve said before, on this issue, women cannot afford to wait any more. We cannot be silent, we cannot depend on the awareness of the occasional, principled CEO and we cannot afford to let another election go by without demanding that political leaders address the wage gap. Nationally, we need strong legislation to end the widespread exploitation of women as a cheap labour force.

We have to recognise that being paid 79 cents on the dollar is only the beginning — the wider impact of the wage gap is that the majority of those living in poverty are women.

An estimated two thirds of all workers in low-wage jobs are single mothers. Many have a hard time feeding their children, and about one in five American children is food-insecure. Mothers struggle to pay for childcare or to stay home when a loved one is sick.

And in many cases, if a woman’s partner abuses her, economic instability is the reason that she is less able to leave. For many women, the wage gap is not a matter of having more money in their pockets; it is a matter of survival.

Last year, when I accepted the Academy Award for my role in Boyhood, I decided that I couldn’t let the moment pass without speaking up for women’s equal pay and equal rights — and I knew that my instinct was right when, the next day, a woman came up to me to tell me that her boss had called her in that morning to give her a raise, telling her there was no reason she should be paid less than the men on her job. She started crying, and so did I, remembering a time when I had to make the decision to turn down one of my first real acting jobs because I was pregnant with my first child.

To help women who find themselves in similar situations, our lawmakers must reach across the aisle and create the changes that American families need. Even though voters believe, overwhelmingly, that women should have equal rights, we still have not adopted the Equal Rights Amendment that would guarantee equality of rights under the law. It is an omission that continues to send the message that women deserve less — fewer rights, less protection, less pay.

This year we have heard a lot about women running and women voting, but not much discussion about bread-and-butter issues affecting women’s ability to support their families.

This, despite that elections, from the presidential race on down, will be decided by the nation’s largest voting bloc — women.

Equal Pay Day is a good time to have that conversation.

•Patricia Arquette is an actress and activist