Male co-habiting same-sex couples earn 23% less than married men and 9% less than men who co-habit with a woman, new research released today reveals.

Lesbians are not discriminated against when compared with heterosexual women, the US study found.

The report’s authors conclude that while negative attitudes toward lesbians could affect them, lesbians may benefit from the perception that they are more career-focused and less likely to leave the labour market to raise children than heterosexual women.

According to the study, 18.1 percent of lesbians have children, compared with 49.4 percent of straight women.

“Employers could reasonably infer that a lesbian applicant or current employee will have a stronger attachment to the labour force than will a heterosexual woman,” the authors said.

The research, from the University of New Hampshire Whittemore School of Business and Economics, analysed labour and wage information from more than 91,000 heterosexual and homosexual couples collected by the U.S. Census March 2004 Current Population Survey.

Gay men working in management and traditional blue-collar, male-dominated jobs make less than straight men because they are discriminated against by their employers.

Bruce Elmslie, professor of economics, and his co-author Edinaldo Tebaldi, former assistant professor of economics at UNH now at Bryant University, produced the research, which appears in a Journal of Labour Research article entitled Sexual Orientation and Labor Market Discrimination.

Discrimination against gay men is most pronounced in management and blue-collar, male-dominated occupations such as building and grounds cleaning and maintenance; construction and extraction; and production.

Previous studies of attitudes of heterosexual men toward gay men and lesbians shows that the bias against gay men is much stronger.

Other studies show that gay men are more likely to be the victim of violence because of their sexual identity than lesbians.

The authors cite a number of possible factors as to why gay men experience labour discrimination and lower wages in certain industries. There is strong evidence indicating discrimination is tied to employer and employee bias.

“Employers may disapprove of gay lifestyles and act on this bias in making hiring decisions,” the authors said.

Employers also may discriminate against gay men in response to the desires of the majority of employees. If employers consider mixing heterosexual and homosexual employees distracting and detrimental to productivity, the authors said the employers may consider it profitable to discriminate.

Gay men also may experience labour market discrimination because customers may not want to interact with them, thus influencing hiring practices. “If customers prefer to interact with heterosexual employees, the owner will act on the customer’s taste for discrimination,” the authors said.

Discrimination may also occur as a result of anti-gay attitudes associated with AIDS and misunderstanding as to how HIV is transmitted.

Previous research shows that people with HIV/AIDS have higher rates of absenteeism from work.

The report authors theorise that biased employers may be reluctant to hire gay men because they are concerned about a loss of productivity if a worker becomes infected with HIV/AIDS.

“If employers perceive one group to be generally less productive or more costly than other groups, individual members of the negatively perceived group will receive lower wage offers regardless of their true characteristics,” they said.

In this study, employee/employer bias was the most prevalent and overwhelming indication of discrimination against gay men.

If the discrimination was consumer-based, the discrimination would be more evident in the services industry where there is direct interaction between employees and customers.

If the discrimination was tied to AIDS/HIV status, the distribution of discrimination would be more uniform across industries.

A UK study in 2006 found that gay men were paid around 6% less than heterosexual colleagues.

The findings also showed that lesbians are paid around 11% more than their straight counterparts.

The authors analysed 35 months of data.

Ben Summerskill, chief executive of gay charity Stonewall, questioned the accuracy of the 2006 study.

“It looks at a small cohort of people, 800 in total, in terms of economic data that’s not a good example, there may be gay couples with more that one household, so it may underestimate the level of affluence,” he said.

“Clearly there are gay men who face economic disadvantage, but there are also lesbians who do.”