The ban on transgender people serving in the military announced this week by President Donald Trump would affect about 15,500 service members on active duty or in the National Guard or reserves, according to a UCLA think tank.

According to the Williams Institute, a UCLA School of Law think tank focused on sexual-orientation and gender-identity law and public policy, about 134,400 transgender adults are military veterans or retirees, meaning roughly 150,000 transgender people have served in the military or are on active duty.

The institute disputed Trump’s assertion that having transgender service members burdens the military “with tremendous medical costs.” A recent Williams Institute study found that employers—including large, self-insured companies—reported “little to no costs” from transition-related healthcare for employees. The institute also cited a RAND Corp. study that estimated transition-related health costs in the military of up to $8.4 million per year, which represents 0.13 percent of the annual $6 billion healthcare costs for active-duty service members.

Jody Herman, scholar of public policy at the institute, said studies have consistently shown that transgender people serve in the military at rates higher than the general population.