Sigh–every Mother's Day, along with the bouquets and the breakfast in bed comes the media chin-puller complaining that working mothers don't make as much money as working fathers.

This year, it's Claire Cain Miller in the New York Times, with this opinion piece: "The Gender Pay Gap Is Largely Because of Motherhood."

What's interesting about Miller's piece is that she, like her fellow liberal pundit, Hanna Rosin, accepts the fact that the reason women might make "77 cents for every man's dollar" (or whatever the current percentage is these days) has more to do with women's work-life balance choices than with actual sex discrimination: Women, especially mothers of small children often choose to work shorter, overtime-free work weeks in less stressful job specialties so they can devote themselves to their families.

Says Miller:

When men and women finish high school, they're paid pretty much equally. But a gender pay gap soon appears, and it grows significantly over the next two decades:

So what changes? The answer can be found by looking at when the pay gap widens most sharply, It's in the late 20s and mid-30s, according to two new studies–in other words, when many women have children. Unmarried women without children continue to earn closer to what men do.

But Miller says: We still ought to pay working mothers the same as working fathers…just because:

To achieve pay equality, social scientists say–other than women avoiding marriage and children–changes would have to take place in workplaces and public policy that applied to both men and women. Examples would be companies putting less priority on long hours and face time, and the government providing subsidized child care and moderate parental leave.

Leaving aside the question of the question of how paying other people to spend more time with one's children would help mothers who want to spend more time with their children themselves, Miller, in the name of "pay equality," is essentially asking employers to pay working mothers for work they don't do. What if "long hours"–staying up all night to put together a legal brief or to handle a sudden surge in demand for your company's product–is simply part of the job? There's a reason why people who work overtime earn more money than those who don't. It's called producing more work. Why shouldn't people who work more earn more?

And there are good economic and non-economic reasons why a typical husband-wife division of labor can involve the husband's putting in the time and enduring the strees of a difficult job to bring home the bacon while the wife puts in shorter, less stressful hours at the jobsite but has time to spend with the kids and make the house a pleasant home. Everybody often benefits from this supposedly "unequal" relationship: husband, wife, and children. The family, as many pundits have pointed out, is the only form of socialism ("each according to his ability, each according to his need…") that actually works.

But Mother's Day invariably brings out the complainers–and their complaints are typically about motherhood itself.