The report examined data and thought leadership materials from a wide range of sources, including the American Association of University Women, the Institute for Women's Policy Research, the Independent Women's Forum and the National Organization for Women.

There was general agreement that the past is what continues to hold down pay for women, because when a prospective employer sets a salary for a new hire, the employer generally gauges that figure to what the person was currently earning.

But establishing a legislative ban on employers' questions about salary history won't be easy to do, most parties agreed.

NOW's Terry O'Neill said it is the single most important action that remains to be taken to level the salary playing field. When a woman agrees early in her career to take less in salary because of her history, "It makes her first experience with being underpaid get kind of baked into the cake of her entire career."

Clinton has fought for gender equality in pay for years, introducing a bill during her Senate career that would have addressed the salary disclosure loophole. The measure was last brought up and then blocked by the GOP in 2014.

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She packages the law as not only the right thing to do from an equality standpoint, but a measure that would boost the nation's economy.

"Guaranteeing equal pay won't just increase paychecks for women — it will boost family budgets and get incomes rising across the board," she said in a speech in Michigan.

Her opponent, Donald Trump, has been hard to pin down on the matter — one more issue where the real estate magnate seems unable to make up his mind.

But most experts interviewed for the CBS report says there's no simple political solution to a problem that has defied policymakers for 50-plus years.

"There are a hundred different things that we can claim are the cause of women's lower average earnings, relative to men, of equal, observable ability, education, skill," says Claudia Goldin, an economics professor at Harvard University. "For each one of these, we play the game of whack-a-mole and say, 'I'm going to fix this one and fix this one,' where the problem is something completely different."