Interestingly, the pay-gap trends examined in the Canadian study were especially strong in high-paying jobs. For example, straight men in senior management on average made about $183,000 each year, while the average for gay men was about $121,000. (Both of those figures are in Canadian dollars.)

The study, done by two Ph.D. candidates in sociology at McGill University, Sean Waite and Nicole Denier, has one major caveat: It only looked at white men and women, because there are significant employment-related hurdles for people of color that would be hard to control for in the data. (Waite told me that he and Denier have plans to examine how ethnicity interacts with sexual orientation in the labor market.)

Their findings—that gay men make less money than straight men and lesbians make more money than straight women—have been demonstrated before. One major review in 2007 found that gay and bisexual men earn between 10 and 32 percent less than similarly qualified heterosexual men, and other studies have found that lesbians on average out-earn straight women. So what might explain those gaps?

For one thing, it’s a matter of education. Waite and Denier found that gay people were nearly twice as likely to hold a bachelor’s degree than straight people—a level of education that tends to grant them some of the best-paying occupations, such as lawyers, psychologists, and managers. In fact, gay men and lesbians were overrepresented among the 15 highest-paying jobs.

At the same time, gay people, it appears, tend to lean toward jobs in different industries than straight people. Gay men, for example, are less likely to go into science or engineering jobs than straight men; lesbians, on the other hand, are less likely to work in the retail industry. Indeed, a 2013 study found that gay people were more likely than straight people to take jobs that were atypical for their gender.

But the jobs they end up taking, it turns out, are where the wage gaps were biggest. “One of the arguments that we put forward is that the remuneration practices in some of the most highly paid occupations…are more dependent on merit and performance pay,” Waite says. “These types of remuneration may allow for more arbitrary evaluation, from both bosses or coworkers, of an employee's worth. In other words, there may be more avenues for conscious or unconscious bias.”

Because Waite and Denier’s data set comes from the big-picture perspective of the Canadian census, they’re hesitant to chalk the wage gap entirely up to discrimination. That said, there’s a strong case to be made that gay men are paid less and lesbian women are paid more because of the biases of those making hiring and compensation decisions. Some studies have suggested that gay men receive fewer interview offers and that discretionary wage increases may produce compensation imbalances.