Transgender and gender-nonconforming individuals face pervasive housing discrimination, according to a recent study. It’s worse than researchers expected, and the people being discriminated against may not even know it.

Researchers at the Suffolk University Law School Housing Discrimination Testing Program in Boston used a pretty straightforward test to determine this. A trans or gender-nonconforming person would respond to a housing rental ad, and then another individual who had similar characteristics but was not trans would go see the same unit. Researchers compared their treatment.

When trying to rent an apartment, the first group received discriminatory treatment 61 percent of the time, the study found.

To make sure the person showing the apartment knew a prospective tenant was transgender, testers were trained to bring up their identity casually, like sharing that their legal name would be different for a credit check.

Thirty-three teams of two people, who worked separately and did not meet, participated in these “matched paired housing discrimination tests” from December 2015 to June 2016, checking out apartments identified in a randomized listing search for studios and one-bedrooms in the Boston area. Testers answered a long list of questions about the experience, like whether they were offered an application or shown other available units. There were major differences in some answers.

Trans and gender-nonconforming individuals were 21 percent less likely to be offered a financial incentive to rent, and 9 percent more likely to be quoted a higher price. They were 12 percent more likely to be told negative comments about the apartment or neighborhood, and 27 percent less likely to be shown extra facilities, like a laundry room or pool.

In one pairing, a tester was told the security deposit would cost four times more than the price offered to the control subject.

“It’s really shocking to see that people are being quoted a higher rental price. That’s just wrong,” study author Jamie Langowski, clinical fellow and assistant director of Suffolk’s Housing Discrimination Testing Program, told The Huffington Post.

It’s legal to discriminate against LGBTQ people in most states. Massachusetts and 19 other states, however, outlaw gender identity-based housing discrimination.

The study adds to evidence that the housing industry, which has a long history of now-outlawed forms of discrimination, allows bias against LGBTQ individuals to flourish, even in states where it’s illegal. A National Center for Transgender Equality survey of trans individuals in 2015 found that 23 percent experienced housing discrimination in the previous year.

None of the testers in the Boston study were explicitly prevented from renting, and some of the individual differences seem minor ― like a control tester being told the kitchen would be freshly painted before moving in, while the other individual was not. But they stacked up to a clear pattern of discriminatory treatment, said Langowski and coauthor William Berman, law professor and director of the testing program.

Part of the problem is that it can be “discrimination with a smile,” Langowski said, so potential renters may be unaware of mistreatment.

Berman and Langowski argue that their study demonstrates the need for federal law preventing housing discrimination based on gender identity.

But under President Donald Trump, there’s already been a rollback of LGBTQ legal protections. Trump signed legislation this week that weakens rules protecting lesbian, gay, bisexual, transgender and queer federal contractors from discrimination. Earlier this month, the administration withdrew a policy that prevented schools from discriminating against transgender students.

With a flurry of discriminatory legislation under consideration and an uptick in hate crimes against transgender individuals, housing discrimination ― widespread, but often subtle ― might not be advocates’ biggest concern. But Berman argued it’s nevertheless an urgent issue.

“There are significant consequences if you lose the ability to live where you want to live only because of who you are,” Berman said. “It affects every part of your life. It affects your ability to have economic opportunities, like commute or proximity to work, health, proximity to health care, education ... so even if you don’t know it, you’ve lost a very significant opportunity.”

Berman and Langowski acknowledged that 33 pairs is a small sample size, but said it’s still the largest study of its kind and produced statistically significant results. The research was conducted in partnership with the city of Boston and funded by a grant from the U.S. Department of Housing and Development.

“Are we concerned when we see budgets that require significant cuts? Absolutely,” Berman said, “because the work is important and we want to see it continue.”