Full-time female managers earned less than their male counterparts in all 10 fields in 1995 and 2000, the General Accounting Office found. In seven of the fields, the earnings gap grew during the five-year period.
The report suggests that women still struggle to break through the "glass ceiling" that historically has been a barrier to advancement in the workplace.
"I don't find one line of good news in the report," said Rep. Carolyn Maloney, D-N.Y. "Yet I think people believe women are doing better."
Maloney and Rep. John Dingell, D-Mich., discussed the report with female journalists invited to a luncheon Wednesday. The lawmakers are releasing it to the public on Thursday.
The report does not explain why earnings may have dropped for women managers. It noted that the pay gap was widest among parents, and that women find it harder to balance children and a career.
Among married managers, nearly 60 percent of men have children at home, compared to 40 percent of women.
The 10 industries examined in the report by the GAO, the investigative arm of Congress, employ 71 percent of female workers and 73 percent of female managers in the United States.
For example, female managers in the communications industry made 86 cents for every dollar earned by male managers in 1995. Five years later, a woman in the same field made 73 cents for every dollar earned by a man, the GAO found.
There were drops in entertainment and recreations services; finances, insurance and real estate; business and repair services; retail trade; and other professional services.
Women's earnings compared to men increased in three fields - public administration, hospitals and medical services and educational services - according to the data.
But according to Census Bureau figures, women are making their way into managerial positions. There were more than 7.1 million women in full-time executive, administrative or managerial positions in 1998 - a 29 percent jump from 1993.
Approximately 9.4 million men held the same kinds of positions, but that represented only a 19 percent increase.
More recent Census data will be available this fall, according to the authors of the GAO report.
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