Kay Hymowitz has a useful piece [1] in the US website, City Journal explaining the phenomenon of the gap in 
income between men and women.
Hymowitz acknowledges that the gap exists, but rejects the notion that it is because of policy failures on the part of government.
Instead, she says that the main driver of the pay gap is that men and women want different things.
Hence, men tend to work longer hours, and women tend to be more likely to favour part-time work.
She cites a number of figures to back this claim.
US figures from 2007 showed that 27 percent of male full-time workers had workweeks of 41 or more hours, compared with 15 percent of female full-time workers; meanwhile, just four percent of full-time men worked 35 to 39 hours a week, while 12 percent of women did.
A 2001 study in the Journal of the American Pharmacists Association showed that male pharmacists worked 44.1 hours a week, on average, while females worked 37.2 hours.
While she acknowledges that this study is a bit dated, she argues that “that things haven’t changed much in the last decade”.
According to a 2009 article in the American Journal of Pharmaceutical Education, female pharmacists’ preference for reduced work hours is enough to lead to an industry labor shortage.
She also rubbishes the claim that women make less than men doing the same jobs, arguing that the official figures don’t break the figures down in sufficient detail to verify that conclusion.
For example, the figures show that among “physicians and surgeons,” “women make only 64.2 percent of what men make.
But Hymowitz points out that “there are dozens of specialties in medicine: some, like cardiac surgery, require years of extra training, grueling hours, and life-and-death procedures; others, like pediatrics, are less demanding and consequently less highly rewarded”.
She writes: “Only 16 percent of surgeons, but a full 50 percent of pediatricians, are women. So the statement that female doctors make only 64.2 percent of what men make is really on the order of a tautology, much like saying that a surgeon working 50 hours a week makes significantly more than a pediatrician working 37”.
The reason that women are inclined to work fewer hours is because women have children, she says.
According to the figures she cites, “if you consider only childless women, the wage gap disappears”.
According June O’Neill, an expert on the wage gap between women and men single, childless women make about eight percent more than single, childless men do (though the advantage vanishes when you factor in education). Once children arrive, women work fewer hours and their wage parity or advantage disappears.
Hymowitz says that the notion that this is because men refuse to do their share of housework, and that women would work more hours if it weren’t for sexist social norms isn’t borne out by the data.
“According to a 2007 Pew Research survey, only 21 percent of working mothers with minor children want to be in the office full-time. Sixty percent say that they would prefer to work part-time, and 19 percent would like to give up their jobs altogether. For working fathers, the numbers are reversed: 72 percent want to work full-time and 12 percent part-time,” she points out.
And this preference appears to be global, she says.
“Look at Iceland, recently crowned the world’s most egalitarian nation by the World Economic Forum. The country boasts a female prime minister, a law requiring that the boards of midsize and larger businesses be at least 40 percent female, excellent public child care, and a family leave policy that would make NOW members swoon.
“Yet despite successful efforts to get men to take paternity leave, Icelandic women still take considerably more time off than men do. They also are far more likely to work part-time. According to the Organisation for Economic Co-operation and Development (OECD), this queen of women-friendly countries has a bigger wage gap—women make 62 percent of what men do—than the United States does.”
In other words, the pressure to provide more and more State subsidised childcare and get more women into fulltime work isn’t coming from most working women, it’s coming from feminist ideologues.