Women are the only or primary breadwinners in 40% of households with children younger than 18 and 63% of those homes are headed by single mothers, according to a new study by the Pew Research Center. In 1960, women accounted for just 11% of the main or sole earners in homes with children.

There is a huge wage gap between the single and married mothers, the study found. The median total family income of married mothers who earn more than their husbands was nearly $80,000 in 2011, well above the national median of $57,100 for all families with children, and nearly four times the $23,000 median for families led by single mothers.

If women received equal pay, both married and single women would be quite a bit better off because women get paid just 77 cents for every $1 men get paid. The picture is even worse for women of color. And the numbers haven’t budged in more than a decade.

The Paycheck Fairness Act (S. 84 and H.R. 377) would close loopholes in current equal pay laws that make it easier for employers to discriminate against women by paying them less. The legislation was blocked by a Republican filibuster last year and reintroduced in January. Urge your representatives to pass the Paycheck Fairness Act.

The study does not examine the wage difference between women who hold union jobs and those employed in nonunion workplaces. But in 2012, according to U.S. Bureau of Labor Statistics figures, the median weekly paycheck for a woman working in a job with a collective bargaining agreement was $877 vs. $663 for women in nonunion jobs. That union difference cuts across occupations, too.

In addition, unionized workers are 54% more likely to have employer-provided pensions. More than 83% of union workers have jobs that provide health insurance benefits, but only 62% of nonunion workers do.

Read the full Pew Research study, and learn more about what the study means in this PBS interview with Ellen Galinsky, president and co-founder of the Families and Work Institute.