Early this past spring, the White House Council on Women and Girls released a much-anticipated report called Women in America. One of its conclusions struck a familiar note: today, as President Obama said in describing the document, “women still earn on average only about 75 cents for every dollar a man earns. That’s a huge discrepancy.”

It is a huge discrepancy. It’s also an exquisite example of what journalist Charles Seife has dubbed “proofiness.” Proofiness is the use of misleading statistics to confirm what you already believe. Indeed, the 75-cent meme depends on a panoply of apple-to-orange comparisons that support a variety of feminist policy initiatives, from the Paycheck Fairness Act to universal child care, while telling us next to nothing about the well-being of women.

This isn’t to say that all is gender-equal in the labor market. It is not. It also isn’t to imply that discrimination against women doesn’t exist or that employers shouldn’t get more creative in adapting to the large number of mothers in the workplace. It does and they should. But by severely overstating and sensationalizing what is a universal predicament (I’m looking at you, Sweden and Iceland!), proofers encourage resentment-fueled demands that no government anywhere has ever fulfilled—and that no government ever will.

Let’s begin by unpacking that 75-cent statistic, which actually varies from 75 to about 81, depending on the year and the study. The figure is based on the average earnings of full-time, year-round (FTYR) workers, usually defined as those who work 35 hours a week or more.

But consider the mischief contained in that “or more.” It makes the full-time category embrace everyone from a clerk who arrives at her desk at 9 am and leaves promptly at 4 pm to a trial lawyer who eats dinner four nights a week—and lunch on weekends—at his desk. I assume, in this case, that the clerk is a woman and the lawyer a man for the simple reason that—and here is an average that proofers rarely mention—full-time men work more hours than full-time women do. In 2007, according to the Bureau of Labor Statistics, 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 4 percent of full-time men worked 35 to 39 hours a week, while 12 percent of women did. Since FTYR men work more than FTYR women do, it shouldn’t be surprising that the men, on average, earn more.

The way proofers finesse “full-time” can be a wonder to behold. Take a recent article in the Washington Post by Mariko Chang, author of a forthcoming book on the wealth gap between women and men. Chang cites a wage difference between “full-time” male and female pharmacists to show how “even when they work in the same occupation, men earn more.” A moment’s Googling led me to a 2001 study in the Journal of the American Pharmacists Association concluding that male pharmacists worked 44.1 hours a week, on average, while females worked 37.2 hours. That study is a bit dated, but it’s a good guess 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.

The other arena of mischief contained in the 75-cent statistic lies in the seemingly harmless term “occupation.” Everyone knows that a CEO makes more than a secretary and that a computer scientist makes more than a nurse. And most people wouldn’t be shocked to hear that secretaries and nurses are likely to be women, while CEOs and computer scientists are likely to be men. That obviously explains much of the wage gap.

But proofers often make the claim that women earn less than men doing the exact same job. They can’t possibly know that. The Labor Department’s occupational categories can be so large that a woman could drive a truck through them. Among “physicians and surgeons,” for example, women make only 64.2 percent of what men make. Outrageous, right? Not if you consider 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. 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.

A good example of how proofers get away with using the rogue term “occupation” is Behind the Pay Gap, a widely quoted 2007 study from the American Association of University Women whose executive summary informs us in its second paragraph that “one year out of college, women working full time earn only 80 percent as much as their male colleagues earn.” The report divides the labor force into 11 extremely broad occupations determined by the Department of Education. So ten years after graduation, we learn, women who go into “business” earn considerably less than their male counterparts do. But the businessman could be an associate at Morgan Stanley who majored in econ, while the businesswoman could be a human-relations manager at Foot Locker who took a lot of psych courses. You don’t read until the end of the summary—a point at which many readers will have already Tweeted their indignation—that when you control for such factors as education and hours worked, there’s actually just a 5 percent pay gap. But the AAUW isn’t going to begin a report with the statement that women earn 95 percent of what their male counterparts earn, is it?

Now, while a 5 percent gap will never lead to a million-woman march on Washington, it’s not peanuts. Over a year, it can add up to real money, and over decades in the labor force, it can mean the difference between retirement in a Boca Raton co-op and a studio apartment in the inner suburbs. Many studies have examined the subject, and a consensus has emerged that when you control for what researchers call “observable” differences—not just hours worked and occupation, but also marital and parental status, experience, college major, and industry—there is still a small unexplained wage gap between men and women. Two Cornell economists, Francine Blau and Lawrence Kahn, place the number at about 9 cents per dollar. In 2009, the CONSAD Research Corporation, under the auspices of the Labor Department, located the gap a little lower, at 4.8 to 7.1 percent.

So what do we make of what, for simplicity’s sake, we’ll call the 7 percent gap? You can’t rule out discrimination, whether deliberate or unconscious. Many women say that male bosses are more comfortable dealing with male workers, especially when the job involves late-night meetings and business conferences in Hawaii. This should become a smaller problem over time, as younger men used to coed dorms and female roommates become managers and, of course, as women themselves move into higher management positions. It’s also possible that male managers fear that a female candidate for promotion, however capable, will be more distracted by family matters than a male would be. They might assume that women are less able to handle competition and pressure. It’s even possible that female managers think such things, too.

No, you can’t rule out discrimination. Neither can you rule out other, equally plausible explanations for the 7 percent gap. The data available to researchers may not be precise; for instance, it’s extremely difficult to find accurate measures of work experience. There’s also a popular theory that women are less aggressive than men when it comes to negotiating salaries.

The point is that we don’t know the reason—or, more likely, reasons—for the 7 percent gap. What we do know is that making discrimination the default explanation for a wage gap, as proofers want us to do, leads us down some weird rabbit holes. Asian men and women earn more than white men and women do, says the Bureau of Labor Statistics. Does that mean that whites are discriminated against in favor of Asians? Female cafeteria attendants earn more than male ones do. Are men discriminated against in that field? Women who work in construction earn almost exactly what men in the field do, while women in education earn considerably less. The logic of default discrimination would lead us to conclude that construction workers are more open to having female colleagues than educators are. With all due respect to the construction workers, that seems unlikely.

So why do women work fewer hours, choose less demanding jobs, and then earn less than men do? The answer is obvious: kids. A number of researchers have found that if you consider only childless women, the wage gap disappears. June O’Neill, an economist who has probably studied wage gaps as much as anyone alive, has found that single, childless women make about 8 percent more than single, childless men do (though the advantage vanishes when you factor in education). Using Census Bureau data of pay levels in 147 of the nation’s 150 largest cities, the research firm Reach Advisors recently showed that single, childless working women under 30 earned 8 percent more than their male counterparts did.

That’s likely to change as soon as the children arrive. Mothers, particularly those with young children, take more time off from work; even when they are working, they’re on the job less. Behind the Pay Gap found that “among women who graduated from college in 1992–93, more than one-fifth (23 percent) of mothers were out of the work force in 2003, and another 17 percent were working part time,” compared with under 2 percent of fathers in each case. Other studies show consistently that the first child significantly reduces a woman’s earnings and that the second child cuts them even further.

The most compelling research into the impact of children on women’s careers and earnings—one that also casts light on why women are a rarity at the highest levels of the corporate and financial world—comes from a 2010 article in the American Economic Journal by Marianne Bertrand of the University of Chicago and Claudia Goldin and Lawrence Katz of Harvard. The authors selected nearly 2,500 MBAs who graduated between 1990 and 2006 from the University of Chicago’s Booth School of Business and followed them as they made their way through the early stages of their careers. If there were discrimination to be found here, Goldin would be your woman. She is coauthor of a renowned 2000 study showing that blind auditions significantly increased the likelihood that an orchestra would hire female musicians.

Here’s what the authors found: right after graduation, men and women had nearly identical earnings and working hours. Over the next ten years, however, women fell way behind. Survey questions revealed three reasons for this. First and least important, men had taken more finance courses and received better grades in those courses, while women had taken more marketing classes. Second, women had more career interruptions. Third and most important, mothers worked fewer hours. “The careers of MBA mothers slow down substantially within a few years of first birth,” the authors wrote. Though 90 percent of women were employed full-time and year-round immediately following graduation, that was the case with only 80 percent five years out, 70 percent nine years out, and 62 percent ten or more years out—and only about half of women with children were working full-time ten years after graduation. By contrast, almost all the male grads were working full-time and year-round. Furthermore, MBA mothers, especially those with higher-earning spouses, “actively chose” family-friendly workplaces that would allow them to avoid long hours, even if it meant lowering their chances to climb the greasy pole.

In other words, these female MBAs bought tickets for what is commonly called the “mommy track.” A little over 20 years ago, the Harvard Business Review published an article by Felice Schwartz proposing that businesses make room for the many, though not all, women who would want to trade some ambition and earnings for more flexibility and time with their children. Dismissed as the “mommy track,” the idea was reviled by those who worried that it gave employers permission to discriminate and that it encouraged women to downsize their aspirations.

But as Virginia Postrel noted in a recent Wall Street Journal article, Schwartz had it right. When working mothers can, they tend to spend less time at work. That explains all those female pharmacists looking for reduced hours. It explains why female lawyers are twice as likely as men to go into public-interest law, in which hours are less brutal than in the partner track at Sullivan & Cromwell. Female medical students tell researchers that they’re choosing not to become surgeons because of “lifestyle issues,” which seems to be a euphemism for wanting more time with the kids. Thirty-three percent of female pediatricians are part-timers—and that’s not because they want more time to play golf.

In the literature on the pay gap and in the media more generally, this state of affairs typically leads to cries of injustice. The presumption is that women pursue reduced or flexible hours because men refuse to take equal responsibility for the children and because the United States does not have “family-friendly policies.” Child care is frequently described as a burden to women, a patriarchal imposition on their ambitions, and a source of profound inequity. But is this attitude accurate? Do women want to be working more, if only the kids—and their useless husbands—would let them? And do we know that more government support would enable them to do so and close the wage gap?

Actually, there is no evidence for either of these propositions. If women work fewer hours than men do, it appears to be because they want it that way. About two-thirds of the part-time workforce in the United States is female. 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.

In fact, women choose fewer hours—despite the resulting gap in earnings—all over the world. That includes countries with generous family leave and child-care policies. 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.

Sweden, in many people’s minds the world’s gender utopia, also has a de facto mommy track. Sweden has one of the highest proportions of working women in the world and a commitment to gender parity that’s close to a national religion. In addition to child care, the country offers paid parental leave that includes two months specifically reserved for fathers. Yet moms still take four times as much leave as dads do. (Women are also more likely to be in lower-paid public-sector jobs; according to sociologist Linda Haas, Sweden has “one of the most sex-segregated labor markets in the world.”) Far more women than men work part-time; almost half of all mothers are on the job 30 hours a week or less. The gender wage gap among full-time workers in Sweden is 15 percent. That’s lower than in the United States, at least according to the flawed data we have, but it’s hardly the feminist Promised Land.

The list goes on. In the Netherlands, over 70 percent of women work part-time and say that they want it that way. According to the Netherlands Institute for Social Research, surveys found that only 4 percent of female part-timers wish that they had full-time jobs. In the United Kingdom, half of female GPs work part-time, and the National Health Service is scrambling to cope with a dearth of doctor hours. Interestingly enough, countries with higher GDPs tend to have the highest percentage of women in part-time work. In fact, the OECD reports that in many of its richest countries, including Denmark, Sweden, Iceland, Germany, the U.K., and the U.S., the percentage of the female workforce in part-time positions has gone up over the last decade.

So it makes no sense to think of either the mommy track or the resulting wage differential as an injustice to women. Less time at work, whether in the form of part-time jobs or fewer full-time hours, is what many women want and what those who can afford it tend to choose. Feminists can object till the Singularity arrives that women are “socialized” to think that they have to be the primary parent. But after decades of feminism and Nordic engineering, the continuing female tropism toward shorter work hours suggests that that view is either false or irrelevant. Even the determined Swedes haven’t been able to get women to stick around the office.

That doesn’t mean that the mommy track doesn’t present a problem, particularly in a culture in which close to half of all marriages break down. A woman can have a baby, decide to reduce her hours and her pay, forgo a pension, and then, ten years later, watch her husband run off with the Pilates instructor. The problem isn’t what it used to be when women had fewer degrees and less work experience during their childless years; women today are in better shape to jump-start their careers if need be. The risk remains, however.

It’s not at all clear how to solve this problem or even if there is a solution, especially during these fiscally challenged days. But one thing is clear: the wage-gap debate ought to begin with the mommy track, not with proofy statistics.