"Why Women Make Less than Men"

"Are we really in the midst of what Pew [Research Center] calls a 'gender reversal'?" asks Kay Hymowitz in the Wall Street Journal. "One stubborn fact of the labor market argues against the idea. That is the gender-hours gap, close cousin of the gender-wage gap." She cites studies from the U.S. to Sweden suggesting that "the famous gender-wage gap is to a considerable degree a gender-hours gap."  Simply put, women more often than not choose to work fewer hours than men once they have children:

The main reason that women spend less time at work than men—and that women are unlikely to be the richer sex—is obvious: children. Today, childless 20-something women do earn more than their male peers. But most are likely to cut back their hours after they have kids, giving men the hours, and income, advantage.