It's not necessarily good news for women. They've talked a lot about the benefits to higher education levels amongst young women, but how much of it is down to a simple selection effect: women that are intelligent, ambitious and career-minded are more likely [quite possibly through choice] to be single and childless in their twenties? Men that are intelligent, ambitious and career-minded don't necessarily need to make the same sacrifices, hence a male cohort of single, childless twentysomethings being quite possibly less valuable to employers than the male one. It's even conceivable that young, single childless women might be both earning more than their male counterparts and still being underpaid relative to their capabilities.