Marriage equality is the law of the land. And now, the push is on for the next frontier of civil rights—transgender rights, including the right to serve openly in the military.

And yet, no one in the military even knows how many have been forced to leave the service for being transgender. In contrast, the U.S. military kept detailed records of how many where discharged for being gay or lesbian.

The U.S. military has never kept such statistics on transgender dismissals, in part, because the system used to document discharge reasons has never had a category for being transgender. At first, it was because there were so few transgender service members, officials assumed there was no need for the category. But in more recent years, as there has been increased visibility of transgender individuals, commanders have masked their discomfort about having transgender troops by providing other reasons for discharge, like medical issues.

Now, as the U.S. military faces increased pressure to eliminate its ban on open transgender service, the absence of such statistics makes it impossible to know not only what effect the current ban has had but also how much lifting of the ban could affect the military. What is the relationship between the number of those discharged for being transgender and those who choose to enlist?

How many transgender service members could need changes in their medical care? How many units could be affected?

Under “Don’t Ask Don’t Tell,” commanders often used someone’s sexual orientation—real or perceived—as an excuse to discharge someone for other reasons. An unpopular female commander would be drummed out as soon as someone learned she was a lesbian, or suspected she was, for example. And fellow soldiers relentlessly hazed men seen as effeminate.

Throughout, the U.S. military kept detailed records of how many where discharged for being gay or lesbian.

But just the opposite happened with those discharged for being transgender; service members will discharged for others reasons to mask a prejudice. A transgender service member would be discharged for being unfit to service, for example, with no mention of their gender identity.

In other words: Being gay or lesbian was used as a weapon with the military judicial system; being transgender in the military is a subject nearly everyone in the chain of command is trying to avoid.

For example, shortly before the repeal of “Don’t Ask Don’t Tell,” Army National Guard Staff Sergeant Rebecca Grant said she was forced to leave when another soldier found out that she identified as a woman. Grant joined the Guard as a man.

The military discharged her for medical reasons, saying she suffered from gender identity disorder.

According to Stars and Stripes, the U.S. Navy may soon require high-level approval before a sailor is discharged for being transgender, much as the U.S. Army and U.S. Air Force already have done.

“The Army and Air Force policy concerning separation of transgender soldiers has not changed. By elevating disposition authority, the action will ensure consistency in the application of existing policy,” said Navy Lieutenant Commander Nate Christensen, a Pentagon spokesman.

That is, the military is pushing for consistency in enforcement—but not in tracking its outcomes.

There is no expectation the U.S. military will begin counting such discharges anytime soon. To create such a category in the current system could signal to some that the military’s ban on transgender service members will continue.

Advocates said the change is inevitable, no matter what the statistic.

Last week, 17 members of the House of Representatives urged Secretary of Defense Ashton Carter to end the department’s “outdated and discriminatory directives and regulations to permit transgender individuals to serve.” The Pentagon did not immediately respond to the letter but has said it is reviewing its so-called “accession policy,” which bars transgender individuals from enlisting or being commissioned in the military.

This month, President Obama hosted a Gay Pride event that include two active-duty service members, including Air Force Senior Airman Logan Ireland, who wore a men’s uniform to the event, reflecting the gender he identifies with. Four veterans, including two in uniform, also appeared at the event.

“The numbers that we already have are more than sufficient to make the changes that need to be made,” said Allyson Robinson, director of policy for SPART*A, an organization of actively serving LGBT members advocating for a change in the military’s current transgender policy. “Having a sense of the numbers would be helpful to drive initiatives after the policy has changed.”

Both Carter and Obama have suggested they are receptive to making a policy change, but they have stopped short of doing it.

Regardless, there is an unease within the ranks, many privately concede.

“The brass is not ready yet,” one senior defense official explained to The Daily Beast “They said we have had enough change for now.”

And yet, the military could be one of the world’s largest employers of those who identify as transgender, according to the findings in one study. The most credible measure of transgender service members in the military was a May 2014 Williams Institute study that found there are roughly 15,000 service members who identify as transgender, out of approximately 1.36 million total (PDF). Among that figure, 6,000 are in the Army.

For all the reluctance to change, that the Navy, Army and Air Force are considering or making changes speaks to a system adjusting its thinking.

“None of the armed services wants to be the last of the services to discharge someone for being transgender,” Robinson said.