The Economist: The Wages Of Sin

LABOUR markets are hotbeds of inequality. For every dollar a white American man in full-time work earns, the average white woman earns 78 cents and the average Latina only 56 cents. Marriage is a boon for male earnings; motherhood drags female earnings down. Likewise, gay men earn about 5% less than heterosexual ones in Britain and France, and 12-16% less in Canada and America, even after controlling for things like education, skills and experience. Yet one minority appears immune to this scourge: lesbians.

Marieka Klawitter of the University of Washington looked at 29 studies on wages and sexual orientation last year.* On average, they found a 9% earnings premium for lesbians over heterosexual women, compared with a penalty of 11% for gay men relative to straight men. This discrepancy has been borne out by research on America, Britain, Canada, Germany and the Netherlands. Even after adjusting for the fact that lesbians are on average more educated than straight women, and less likely to have children, the gap persists.

Research on this topic should be taken with a pinch of salt... 

The Economist.

I don't know about lesbians, but one thing is gay men are more likely to do 'female jobs' (the caring professions, hospitality, retail etc) which tend to be badly paid - and perhaps that's where much of the wage discrepancy comes from?

For more research on this see Joe Clark's Gay Money: The Truth About Lesbian And Gay Economics.