Academy Award winner Patricia Arquette used her 80-second acceptance speech at Sunday night's Oscar ceremony to champion women’s rights, declaring, “it’s our time to have wage equality once and for all!” The crowd roared, with Hollywood royalty such as fellow Oscar winner Meryl Streep cheering in solidarity. Many viewers no doubt did the same at home.

Arquette continued her equality push on Twitter following the Oscars, arguing, among other things that "women have been basically paying a gender tax for generations:"

Women have been basically paying a gender tax for generations. — Patricia Arquette (@PattyArquette) February 23, 2015

Guess which women are the most negatively effected in wage inequality? Women of color. #Equalpay for ALL women. Women stand together in this — Patricia Arquette (@PattyArquette) February 23, 2015

If you are fighting against #Equalpay you are fighting for ALL women and especially women of color to make less money than men. — Patricia Arquette (@PattyArquette) February 23, 2015

There are, in fact, notable disparities in the pay men and women receive—but they’re not quite as deep as some make it sound. Working women have made tremendous strides during the last three decades, and in some fields there’s no longer any gender pay gap at all. Beyond that, young women today are entering the workforce better educated and in general better prepared for the modern economy than men, which will help even out whatever pay gap remains in the future. The best news for working women may be that pay discrimination, while illegal, is also becoming culturally unacceptable, with much stronger support systems for women who risk their jobs or careers by demanding equal pay and fair treatment.

Still, some prominent anecdotal examples fuel the storyline of women battling their Mad Men bosses for the right to be treated the same as men. Hacked emails from Sony Pictures executives, for instance, revealed that megastars Jennifer Lawrence and Charlize Theron earned less than their male counterparts for similar roles in a couple of films. If Hollywood’s leading ladies can’t get a fair shake, how can mid- or entry-level working women? Meanwhile, a sexual discrimination lawsuit involving the high-profile venture capital firm Kleiner Perkins Caufield & Byers seems likely to highlight differing pay and performance standards for men and women in the money machine known as Silicon Valley when it kicks off this week.

Numerically, the gender pay gap clearly exists. It’s generally accepted that women earn just 78% of what men earn, on average. Women’s pay improved sharply during the 1980s and 1990s, but it has stagnated, relative to men’s pay, since then, as this chart from the Institute for Women's Policy Research shows:

Source: Institute for Women's Policy Research More

This trend is distressing on the surface -- it implies that a woman who started in a certain field at the same time as an equally qualified man, and performed just as well, would nonetheless get paid less for her entire career.

But that’s not what is really happening in most cases. Women are more likely to take time off for family reasons, which slows their career development and their rate of pay increases--skewing average pay figures in favor of men. Women are also more likely to work part time or choose flexible arrangements over demanding work more likely to lead to promotions, so they're better able to care for other family members. Put another way, men are more likely to take jobs with grueling hours, which usually pay more.

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