Happy National Equal Pay Day! Yes, it’s a holiday — and Democratic National Committee Chairwoman Debbie Wasserman Schultz has already marked the occasion with an unsubtle jab aimed at GOP presidential hopeful Mitt Romney.

The National Committee on Pay Equity (yes, that exists, too) started Equal Pay Day in 1996 to call attention to the gender wage gap. Here’s the idea: It would take the average working woman all of 2011 plus 2012 up to today, April 17, to earn what the average man would earn in just 2011.

That proves that women often occupy lower-paying jobs than men — but does it really prove that women don’t receive equal pay for equal work? Not necessarily. As LearnLiberty’s Steve Horwitz explains in this video, four crucial differences in the way men and women approach work account for the gender wage gap.

1. Men and women make different educational choices. While men often pursue careers in engineering or other hard sciences, women often pursue careers in the social sciences or the caregiving realm. Some liberals argue that “the pay scale for different occupations is connected to whether or not the occupations are made up of mostly men or mostly women.” (Personally, I find that hard to believe as, once upon a time, primarily men worked in all those occupations, so the different pay scales couldn’t have developed according to whether primarily men or primarily women worked in those occupations.) Sarah Damaske, author of For the Family? How Class and Gender Shape Women’s Work, is one such liberal. “Caregiving, whether done unpaid in the home or for pay outside of it, is not particularly valued in this country and women (whether in the labor market or not) suffer the brunt of this,” she writes. Nevertheless, even Damaske does not argue that occupational differences — many stemming from the different educational choices men and women make — do not account in part for the gender wage gap.
2. Men and women also often have different expectations about their career. A women who does not expect to work when she has her first child or who expects to go part-time when she has her first child makes different career choices than a man who expects to work his entire life.
3. Women are more likely to work part-time than men.
4. Men and women differ in their tenure on a job or the way in which their careers are interrupted.

As Horwitz puts it, until women enter high-paying fields in the same numbers as men and until men share equally responsibility for caring for children, the gender wage gap is likely to persist. “Whatever choices men and women make,” Horwitz says in the video,” the wages they’re paid in the market will reflect the productivity of those choices and are not the result of discrimination.”

I’d argue that it’s OK that a gender wage gap exists, as women likely need and want to be able to trade higher wages for greater flexibility and other perks. Once again, liberals are in the position of suggesting that how much money or material benefits a person receives is more important than intangibles.

When a woman agrees to particular wages for a particular job, she implies by her agreement that she thinks those wages are fair. That assessment really shouldn’t be altered by subsequent knowledge that someone else — whether another woman or a man — receives more. If a woman doesn’t think the pay is fair, she should negotiate for more — or find a job elsewhere.