In the 1960s, Janice Bellace worked as a Bell Telephone operator while she went to college. All Bell Telephone operators were women then.

"Then I realized that men who were hired straight out of high school, of the same intelligence, got paid almost double," she said.

 The positions open to the men were not open to women, even within the same company.

President John F. Kennedy signed the Equal Pay Act into law 50 years ago on June 10. It mandated that women should receive equal pay for equal work at a time when the differences in men and women's earnings were stark.

Bellace, now a lawyer and professor at the Wharton School of Business at the University of Pennsylvania, said  the law was a modest contributor to the changing scene for women in the workplace.

"There were some examples of blatant discrimination where men made more doing the same job but actually men and women weren't doing the same jobs," she said. "They might work in the same place but they were doing different jobs."

That was a drag on progress, confirms Liz Watson of the National Women's Law Center:

"In 1963 the wage gap was 59 cents on the dollar. In 1981, when Bobbie McGee wrote a song called 'Fifty-Nine Cents,' which is this great song, it was still 59 cents," Watson said.

"59 cents for every man's dollar

59 cents that's the name of the game.

59 cents makes a grown woman holler.

They give you a diploma but they treat you the same."

"There was a long period where there was not a lot of progress," observed Watson.

The wage gap narrowed pretty steadily in the 1980s and 1990s, but levelled off in the first decade of the new millennium to around 80 cents, roughly where it stands today, at 77 cents.

Watson says that is because a lot of women work in lower-paying occupations, but it also widens over time as women still handle most care-giving responsibilities.

"You really see woman suffering an economic penalty for taking that time to care for their families," Watson said.

That matters. The Pew Research Center recently found that despite the stalled wage gap, women contribute a larger share of household income, nationally than in the past. Women now make up 40 percent of primary breadwinners in the U.S.