Between 1970 and 2009, according to the Bureau of Labor Statistics, the number of women in the labor force more than doubled. Slightly more than one-third of employed Americans in 1970, women made up almost half of the labor force in 2009. Fewer than one-third held full-time jobs in 1970; more than four in 10 did in 2009.

The rise in the educational credentials of women over the same period was simultaneous, equally transforming and not unrelated.

According to U.S. Department of Education statistics, between 1977 and 2008, the number of women earning associate and bachelor's degrees more than doubled. By 2008, women were earning more than half of all bachelor's, master's and doctoral degrees and a fraction less than half of all professional degrees.

The gains did not come because women were taking the places of men -- the number of men earning bachelor's degrees also rose -- it was just that women were entering higher education in greater numbers. According to the 2010 Chronicle of Higher Education Almanac, by 2008, the most recent year for which figures are available, women made up well over half of the enrollments in two-year institutions, four-year colleges and graduate programs.

Many of the fields of study had direct applications in the workplace. In business, management and marketing, women earned two-thirds of the associate degrees, nearly half of the bachelor's and more than 40 percent of the master's and doctoral degrees. Women earned three-quarters of the professional degrees in veterinary medicine, two-thirds in pharmacy, more than half in optometry and osteopathic medicine, not quite half in medicine, and more than 45 percent in dentistry and law. Women earned more than 40 percent of the bachelor's degrees in the fields of security and protective services, science technology, mathematics and statistics, and the physical sciences.

But the gender gap in wages persists. The Bureau of Labor Statistics reports that in 2010 the median wage of the nearly 100 million women working full time was 81 percent of what men earned.

Skeptics of a wage gap contend that disparity exists because women entered many fields only recently. In time, it will disappear. The argument makes some sense when you look back over three decades at occupations such as physicians and surgeons, where women earn 71 percent of what men do. It makes less sense in the field where the largest number of women are working full time: registered nursing. Nine out of every 10 registered nurses are women. Their annual median income is 87 percent of male registered nurses.

A pay disparity exists in every occupational category. Nine of 10 medical assistants are women. Their median annual wage is 3.6 percent lower than men's. Eight of 10 elementary and middle school teachers are women. They have a median income that is 90 percent of their male colleagues. More than half of all financial managers are women. They earn about two-thirds of what male financial managers make. The six of 10 education administrators who are women confront a 23 percent wage gap. The wage gap is equally visible in fields where the numbers of women are low, such as computer scientists and system analysis (30 percent women, wage gap 28 percent).

One can look at the numbers and claim progress. The current 81 percent gap in the median annual earnings of women working full time compared with men appears better than the 59 percent gap in 1981 and 71 percent in 1998. But at least some of the increase is due to a greater decline in men's earnings in the current recession.

Studies continue to show that higher levels of education translate into greater income, but this is true for men and women, and there is little data to suggest that education closes the wage gap. Starting salaries and job responsibilities are among the strongest reasons for the continued existence of the gap. According to a recent Catalyst study, men were more likely to start their first post-MBA job at a higher level, received salaries that averaged $4,600 more and took their first assignments at a higher rank with greater levels of responsibilities.

The suggestion for women with skills: Avoid a lifetime of lower wages and jobs with less future. Before the job interview, research thoroughly to find out what the men in the position are making, their job titles and the responsibilities they have and find out what the male job candidates are asking for. In the job interview, ask for at least that. Then be prepared to avoid being maneuvered into agreeing that the position you are being offered is "different." It probably isn't.

Dorothy Perrin Moore, Ph.D., is professor emerita of business and entrepreneurship at The Citadel.The Job Coaches are experienced volunteers from the Center for Women's Job Counseling Program. Ask them a question at 763-7333 or email info@c4women.org. If you want further assistance, make a counseling appointment; a donation of $35 is requested.