Gay and lesbian couples searching for an apartment are discriminated against more than heterosexual couples, according to the first large-scale study of its kind.

The study, which involved nearly 7,000 e-mail tests, assessed the treatment of same-sex couples when responding to Internet ads for rental units.

The findings show that heterosexual couples are significantly more likely than their gay male and lesbian counterparts to receive an initial e-mail response. Heterosexual couples received favorable treatment over gay male couples in 15.9 percent of tests and over lesbian couples in 15.6 percent of tests, reports the Department of Housing and Urban Development (HUD).

The research is based on 6,833 e-mail correspondence tests conducted in 50 metropolitan markets from June through October 2011. For each correspondence test, two e-mails were sent to the housing provider, each inquiring about the availability of the unit advertised on the Internet. The only difference between the e-mails was the sexual orientation of the couple making the inquiry. The correspondence from heterosexuals referred to a relationship partner as “husband” or “wife” while those from a gay couple referred to a “partner.” In the case of a gay male couple, two male names were used. Two female names were used when the e-mail came from a lesbian pair.

HUD says this methodology provides the first direct evidence of discrimi­natory treatment of same-sex couples compared with the treatment of heterosexual couples when searching for apartments advertised on the Internet.

The Fair Housing Act makes it illegal to discriminate in rental, sales, and lending on the basis of race, color, national origin, religion, sex, disability, and familial status; however, it does not include sexual orientation or gender identity as protected classes. Nonetheless, 20 states and the District of Columbia, and more than 150 cities, towns, and counties across the nation have laws that specifically prohibit discrimination against LGBT individuals.

It is surprising that the states with legislative protections show slightly more adverse treatment for gay men and lesbians than results in states without protections.

Several factors could account for this finding, including potentially low levels of enforcement, housing provider unfamiliarity with state-level protections, or the possibility that protections exist in states with the greatest need for them, reports the study.

Recently, HUD issued new guidance that treats discrimination based on gender nonconformity or sex stereotyping as sex discrimination under the Fair Housing Act, and instructs HUD staff to inform individuals filing complaints about state and local agencies that have LGBT-inclusive nondiscrimination laws. In addition, on Feb. 3, 2012, HUD published a final rule, “Equal Access to Housing in HUD Programs Regardless of Sexual Orientation or Gender Identity,” which requires HUD-funded and HUD-insured housing providers and FHA-approved lenders to provide equal access without regard to sexual orientation, gender identity, and marital status.

The new study, which was done in collaboration with the University of Albany, State University of New York, serves as the initial step toward future research on same-sex housing discrimination. HUD notes that future studies can employ e-mail or in-person audits to assess treatment between same-sex and heterosexual couples in states with and without legislative protections for sexual orientation or gender identity.

The study, An Estimate of Housing Discrimination Against Same-Sex Couples, can be found here.