When people get married, their labor supply tends to decrease. This may come from the fact that this provides opportunities for specialization in market and home production, in particular through child rearing. When looking at unattached vs. partnered or married individuals, the prediction, and the observation, is thus that the latter work less.
Amélie Lafrance, Casey Warman and Frances Woolley verify this for homosexual individuals. For lesbians, no difference with the rest of the population, but for gays, surprise. Attached or married gays work more. This runs counter to any intuition, except if there is some particular selection into marriage. Puzzling.