BABY GAP.

BABY GAP. I keep reading arguments like this one in today's Wall Street Journal about how differential birthrates will spell doom for liberalism:

Simply put, liberals have a big baby problem: They're not having enough of them, they haven't for a long time, and their pool of potential new voters is suffering as a result. According to the 2004 General Social Survey, if you picked 100 unrelated politically liberal adults at random, you would find that they had, between them, 147 children. If you picked 100 conservatives, you would find 208 kids. That's a "fertility gap" of 41%. Given that about 80% of people with an identifiable party preference grow up to vote the same way as their parents, this gap translates into lots more little Republicans than little Democrats to vote in future elections. Over the past 30 years this gap has not been below 20%--explaining, to a large extent, the current ineffectiveness of liberal youth voter campaigns today.

Differential birthrates really do have this kind of effect in countries like Lebanon where politics is structured around more-or-less closed sects. But an 80 percent retention rate is actually rather low. What's more, partisan self-identification and ideological self-identification are different things, so the relevance of the 80 percent figure is unclear. In addition, pluralities of people self-identify as independents and moderates, but many of those people actually have fixed partisan leanings.

If you just do the straightforward thing and look at actual demographic cohorts, 18-30 year-olds are significantly more likely to vote Democratic than are older people, and have more left-wing views on most issues.

--Matthew Yglesias