Even with all these successes, the federal policy has remained unchanged since Clinton signed it a quarter-century ago. The United States still holds the unenviable title of being the only industrialized country that does not offer all of its citizens paid family leave. According to the US Bureau of Labor Statistics, only 14% of civilian workers had access to paid leave in 2016, and that's only thanks to state laws or employer largess.

Even as they've expanded in recent years, the laws protecting pregnant women at work are patchwork and continue to leave out a lot of women, Gedmark said. Discriminating against pregnant women is clearly illegal. But whether a business has to accommodate pregnant women, by giving them a stool to sit on or allowing them more water breaks, remains unclear. Different states have different standards for what kinds of accommodations pregnant workers are legally entitled to receive. Furthermore, the definition of what can be considered a pregnancy-related disability, and therefore requires accommodations, remains elusive among lawmakers on the federal level, as well as in states that lack clear protections.

Employers tend to provide workers control over their work when they trust and believe that will contribute back to the company rather than to skive off work. As a result, this control is rewarded only to high-skill workers in top occupations. Since society still holds rather gendered views of men and women—believing that men’s priorities lies in breadwinning while women will prioritize their family life, employers are more reluctant to provide control over work time to women, believing they will use it to care for their families rather than use it to improve their work performance.

"Probably the biggest burden is child care," Bovino told CNBC. While she credits men today with helping more, "women (still) do the lion's share of child care and elder care as well." Maternity and family leave also impacts the decision for women to rejoin the workforce, she added. Bovino said the S&P study found that 39 percent of mothers took "a lot of time out of the workforce when they have children, and 25% don't come back." Her research found 24 percent of fathers take significant time off for child or family care.

Amazon’s decision follows the passage of several state and local laws banning employers from asking interviewees how much they’re compensated. California, where many of Amazon’s big tech competitors have their headquarters, passed a salary history law in October that went into effect at the beginning of this year.

"When we modelled the factors that influence pay, the results showed that both men's and women's pay grow for most of their lives. "Overall, women's pay grows less than men's and also stops growing earlier than men's pay. This applies to both the private and public sectors."

Many of the initiatives to try to attract and retain female staff have been launched in the past few years and some private equity firms have only recently started to track the proportion of women in the workforce.Pressure is growing on employers in the financial services industry to hire more women and reduce the pay gap between male and female workers, as investors seek more diversity of views in the hope that this will boost returns.

The first industrial revolution introduced the modern construct of gender, stereotyping men as “breadwinners” and women as “homemakers.” Since then, two more industrial revolutions have followed, both of which have reinforced these sexist tropes. We have now arrived at the fourth—and this revolution has the opportunity to dismantle gender stereotypes all together.

As a matter of justice we obviously owe equal pay for equal work. As a matter of return on human capital investment, however, it is clear that the marketplace won’t pay for work experience keeping a home. It is also clear that child bearing and rearing cuts into career development for women trying to balance the two.

The lack of accommodation for women’s caregiving responsibilities is one of the reasons they are not promoted into leadership. Colleagues may assume, without verification, that caregivers need certain costly accommodations or are simply unavailable (“Let’s not ask her to do this because she is breastfeeding.”) The absence of a field-wide discussion on the actual adjustments necessary is leading to career stagnation among talented and ambitious professionals and to a wide gender imbalance in leadership.

“At first, it felt as if the term had the potential to change everything,” she wrote in the New York Times. “But…the term, which once held so much promise, has been co-opted, sanitized, stripped of its power to shock, disturb and galvanize.” Over the years, Farley watched in dismay as the phrase became a standard part of corporate orientation sessions, intended for businesses to defend themselves against lawsuits by female employees. “The working women’s revolution I once envisioned hasn’t happened,” she wrote recently. Though Farley recognizes that the term has sparked change in the workplace, she feels it did little to change the power dynamics that allow harassment to flourish.