At least for the childless among our generation (Gen Y and Millennials), once you account for differences in hours worked, choice of professions, and willingness to ask for raises and promotions, the gap pretty much disappears. Throw children into the mix, however, and the gap explodes to, in some demographics (e.g. single mothers), as high as 50%: www.bls.gov/opub/mlr/2014/beyo… (and other charts on the site) Make no mistake, this is discrimination—not against women in general, but against parents, particularly mothers. (Generally because of traditional divisions of labor, married fathers are hardly affected, but what little info exists on single fathers suggests they're hit almost as hard as single mothers.)
So this is the conversation we need to be having: what can businesses and society do to make it so that having children stops disproportionately holding women back in their careers? It's a far less tractable problem than simple sex discrimination: the solutions will need to be many-pronged, will have to combat many deep-seated prejudices in who society says is responsible for childcare, and most importantly, will have to overwhelm the monetary and political resistance from corporations more hostile to labor-rights than at any time in the last 50 years.
Ironically, corporations have financial incentives play along as the sexist villains with the straightforward 78-cents-on-the-dollar narrative, because most of them have already solved that problem. They don't have to do anything, and the chronically-distracted public (distracted by their personal, familial, and financial struggles for the most part) will be satisfied that the solution is as simple as beefing up enforcement of the Equal Pay Act. If the public did their research and demanded their employers walked the "family-friendly" walk, it would take a hefty bite out of corporate profits (which, need I remind you, kept on climbing to historic highs right through the Recession) to offer equitable paid parental leave, living wages, flexible hours, full healthcare coverage, and other benefits that are standard in civilized nations with adequate social safety nets. Good social safety nets are widely known by researchers to be strongly tied to lower rates of child abuse and domestic violence, BTW (one big reason America sees so much more DV than Western Europe www.washingtonpost.com/blogs/w… ). It's shocking how many of our nation's problems come back to the fact that we live in a corporatocracy guided by the principles of