Women continue to struggle for equal pay in the workplace. For at least two decades, they have earned 80% of the wages of men doing equivalent jobs. That should be a shock to most people, since the feminist movement is several decades old. Sadly though, the financial gains that women have made have eroded in recent years.

"The ratio of women's and men's median annual earnings was 77.0 for full-time, year-round workers in 2009, essentially unchanged from 77.1 in 2008. (This means the gender wage gap for full-time, year-round workers is now 22.9 percent.) This is below the peak of 77.8 percent in 2007," according to the Institute for Women's Policy Research.

We analyzed data from the Bureau of Labor Statistics, the Department of Labor, the Census Bureau, Catalyst (the leading nonprofit organization for expanding women in business), and The Institute for Women's Policy Research, to determine which ten industries have the greatest pay disparity between the sexes. Along with this information, we added other data to shed some light on the issue. According to this research, women earn as little as two-thirds as much money as men do to perform the same job in some industries.

Researchers say that one cause of the ongoing inequality is that some large industries employ far more men than women. This includes utilities, public administration, and the retail trade. There is no clear reason why these industries favor men.

Do men conspire to keep the pay of the women at low levels? No evidence indicates that this has occurred. What about the theory that senior management purposely keeps men's pay higher? There is little proof of this either, though several legal cases make this claim.

"Alas, no one has those data, as companies tend to be very secretive about this," says Arian Hegewisch, Study Director at IWPR. "The best information in theory might be sex discrimination law cases against specific companies, but even there, unless cases are litigated by the EEOC, typically wage and salary data are kept under wraps."

Women may be held back because surprisingly few of them are in senior management at many companies. Catalyst found that women held 15.7% of the board seats in Fortune 500 companies in 2010, an inexplicable statistic given the number of available qualified female candidates. More than 10 percent had no women serving on their boards at all.

Women are not the only group that faces pay discrimination. People of color suffer from similar disadvantages. White men have largely controlled the top-tier of positions in both government and business since the country's founding. Those in power may want people like themselves to remain in power. This could be one, and perhaps the most important, reason for inequality of pay. There is no research, however, that shows that white men consciously decide to underpay women and minorities because it's in their economic self-interest.

See also: How Women in the Workforce Are Changing America

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