It's taken as a given that whatever else has changed over the past couple of generations, women still do the lion's share of the parenting in America. Data backs this up, but with an interesting twist that reveals that American dads have in some ways stepped up more than people realize. Back in 1965, the average woman with a child at home spent 10 hours per week on child care, and the average man with a child at home spent 2.5 hours. To share the burden equally, then, men would need to spend six or seven hours a week on child care.

And by 2011, the average American man with a kid at home was in fact spending seven hours per week on child care.

The reason that the burden isn't even is that while men decided to spend more time with their children, women decided to … also spend more time with their children.

Rather than dads getting more involved and moms taking a bit of a break, dads have gotten a lot more involved with their kids, and moms have gotten even more involved than they were before. When you consider that the average woman has fewer children these days than was the case in the baby boom years, what you're looking at is a drastic increase in the quantity of per-child parenting happening in two-parent households.

Since spending more time with your kids doesn't seem to change much for the kids one way or the other (see books by Judith Rich Harris and Bryan Caplan for the argument in more detail), one hopes parents are at least enjoying the extra child care time.

But whatever the upside of the trend toward more parenting, gender equality has (so far) been one casualty of it. And if you think about it, it's pretty easy to see how society could be stuck in a dysfunctional pattern in this regard. On the one hand, modern dads want to do their fair share. On the other hand, modern moms are laboring under social expectations that assign them primary responsibility for their kids. So if Dad does more, that doesn't so much lower the burden placed on Mom as raise the bar even higher.