Other studies have shown that the divide in earnings may have widened over the last 10 years.

One year after graduation, women made more than men in just one field, engineering, and made at least 90 percent as much in four others, according to a breakdown of findings for 10 professions. Pay in the five remaining disciplines ranged from 75 percent to 88 percent of men's salaries.

"Part of this, we know, is probably gender discrimination," said Sylvia Allegretto, an economist at the Economic Policy Institute who had not yet seen the AAUW study. "But there's also the idea that women are less tied to the labor market."

According to Census Bureau statistics released last year, the pay gap for full-time workers at all education levels was the narrowest ever, with women earning 77 cents for every dollar paid to men. Education Department figures show the share of women attending college rose to 51 percent in 2003, from 33 percent three decades earlier.