Forty percent of legal professionals are women, up from 14 percent in 1975, the Equal Employment Opportunity Commission found in its report on law-firm diversity.
Minorities have gained, too. Twice as many blacks work in the legal profession than did in 1975, and over 4 percent of professionals in law firms are black. Hispanics more than doubled to 3 percent; Asians rose to 6.5 percent, 5 times their percentage in 1975.
Still, more than 60 percent of partners are white men, the study said. Thirteen percent are women, including all races.
"We must all make a constant, unwavering effort to ensure that our nation's law firms are open and inclusive to all individuals," said Cari Dominguez, commission chairwoman.
The research covers medium and large private-sector law firms with 100 or more employees.
The report tracked progress in law schools as well, finding that between 1982 and 2002, among people earning law degrees, women increased from 33 percent to 48 percent; blacks from 4.2 percent to 7.2 percent; Hispanics from 2.3 percent to 5.7 percent; and Asians from 1.3 percent to 6.5 percent.
John J. Donohue III, professor at Stanford Law School, said the larger number of male partners could be attributed in part to women opting for lesser positions in law firms to leave time for families.
"Over time, a lot more women have gone to law school, so that explains the increase of women in the law profession," he said. "But at the same time, the demands of a high-level corporate practice have also risen considerably, and there's a certain number of women who feel the price is too high to pay if one is going to be involved in child-rearing."
Many aspects of federal law have made legal careers more appealing to women. For example, they can no longer be discriminated against when they become pregnant.
The study said the most pressing equal employment issue in large national law firms is no longer hiring but conditions of employment, especially promotion to partnership. In smaller firms, questions about the fairness and openness of hiring practices may still remain, the study said.
Minority legal professionals were most likely to be associated with the largest firms, the commission said.