Not surprisingly, "even when you control for occupation and a host of other variables, economists still find an unexplained gender gap of anywhere from around a nickel to a dime or more on the dollar." Female MBA-graduates, for instance, make about $4,600 less than their male counterparts.
The article expands on a few measures (one that Obama signed into law, one that has slimmer chances of making it through Congress) designed to close the gap, and is very much worth a read or a listen.