show that more than 619 men and women were discharged last year because of their sexual orientation. Of those, one-third were women - even though they account for 15 percent of all active-duty and reserve members.
"It's very clear the military comes down harder on women than on men, but the question of whether they come down harder on lesbians than on gay men is harder to answer," said Aaron Belkin, director of the Palm Center, a University of California, Santa Barbara, center specializing in gays and the military. "We don't know whether the statistics reflect lesbian-baiting or just a higher rate of lesbians in the military."
The Palm Center obtained the statistics from the Pentagon and released them Thursday.
Pentagon spokeswoman Cynthia Smith said officials will not look into the matter because even inquiring about it might violate the 1993 policy, which says gay men and lesbians in the military cannot be investigated or punished as long as they keep their sexual orientation to themselves.
"If we did investigate it, we would have to ask questions, and we aren't supposed to ask any questions," Smith said.
On Saturday, President Barack Obama is scheduled to deliver the keynote address at a fundraising dinner for the nation's largest gay rights group.
Activists have begun to step up pressure on Obama to sign an executive order repealing the gay ban in the military. A White House spokesman said the president "is intent on making progress" on the issue.
In the Army, women accounted for 14 percent of personnel and 36 percent of the "don't ask, don't tell" discharges in 2008; in the Navy, it was 14 percent of the personnel and 23 percent of the discharges, and in the Marines, 6 percent and 18 percent.
The disparity was particularly striking in the Air Force, where women represented 20 percent of all personnel but 61 percent of those expelled. That is a significant jump from the previous year and marks the first time women in any branch of the military constituted a majority of those dismissed under "don't ask, don't tell," researchers said.
In 2007, 49 percent of Air Force personnel discharged for being gay were women.
Some women who served in the military said the gap could be a result of "lesbian-baiting" rumors and investigations that arise when women rebuff sexual overtures from male colleagues or do not meet traditional notions of feminine beauty.
"Often times the lesbians under my command were under scrutiny by the same men who were also sexually harassing straight women, so it was this kind of sexist undercurrent of 'You don't belong here,"' said Anuradha Bhagwati, a former Marine who founded the Service Women's Action Network, an advocacy group.
Julianne Sohn, the lone female Marine officer discharged under the policy last year, was a lieutenant who had served a seven-month tour in Iraq as a reservist when she received a telephone call at home from a lieutenant colonel informing her she was under investigation for being a lesbian.
The call was not a surprise. Some of her fellow Marines, who knew about her sexual orientation, had given her a heads-up a few months before.
Sohn had been speaking publicly about her experience as a gay officer as part of an organized effort to spotlight the costs of "don't ask, don't tell." She said she could not respond honestly when colleagues wanted to know why she did not have a boyfriend, and said she asked her brothers to contact her girlfriend if she were killed in Iraq because she did not want to list a woman as her next of kin.
Sohn, 33, who now works as a police officer in Los Angeles, said hearing the investigating officer read her the military's equivalent of a criminal suspect's Miranda warning over the phone was a fresh insult.
"The way I look at is, all I've done is tell my story," said Sohn, who did not fight the inquiry and was honorably discharged. "I wanted to serve, and I did serve."