On the political left, raising the youth vote is one of the most common goals. This implicitly plays to the tired old axiom that a person under 30 who is not a liberal has no heart (whereas one who is still a liberal after 30 has no head). The trouble is, while most "get out the vote" campaigns targeting young people are proxies for the Democratic Party, these efforts haven't apparently done much to win elections for the Democrats. The explanation we often hear from the left is that the new young Democrats are more than counterbalanced by voters scared up by the Republicans on "cultural issues" like abortion, gun rights and gay marriage.

But the data on young Americans tell a different story. 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.