Economists have spent the last couple centuries scoffing at "just price" theory. Almost everyone now admits that prices have to fluctuate in response to supply and demand; it's silly to insist, for example, that the "just price" of a loan is 0%. But there's one particularly stubborn hold-out: The "just price" theory of relationships. Even the wise Megan McArdle tells us:
[M]uch of the labor illegal immigrants provide substitutes for women's home labor. And I don't just mean nannies for rich women. I mean cleaning services, and food processing, and dry cleaning, and grocery delivery, and all the other things that make it possible for large numbers of women to work outside the home. In an ideal world, of course, women and men would take equal responsibility for the household.
The most obvious flaw in this familiar feminist norm is that it completely ignores comparative advantange. What if a man has a much higher wage than his wife, but can't clean, cook, or shop to save his life? Should he still do half the cleaning, cooking, and shopping? Wouldn't husband and wife alike be better off if he specialized in bringing home the bread, and she specialized in baking it?
Now perhaps Megan interprets "responsibility for the household" to encompass both earning income and doing housework. Correctly stated, the norm might be "A relationship should be 50/50 overall, not on any particular margin." But even this more sophisticated norm totally ignores market forces. What if there are two men for every woman? Men are naturally going to offer a better deal to potential spouses than they would if the gender balance were reversed. What's so bad about that?
In reality, the 50/50 norm is a source of much needless marital strife. The 50/50 norm urges people to ask whether they're getting 50%, and stand up for themselves if they think they aren't. That's a recipe for pointless conflict with the person you love. Who cares if you're getting 50%, if you're getting what you bargained for?
P.S. When was the last time the 50/50 norm was invoked to justify better treatment of a man? I sense a pattern.