James Taranto writes on the Wall Street Journal site:
Compounding the GOP advantage is what I call the Roe effect. It is a statement of fact, not a moral judgment, to observe that every pregnancy aborted today results in one fewer eligible voter 18 years from now. More than 40 million legal abortions have occurred in the United States since 1973, and these are not randomly distributed across the population. Black women, for example, have a higher abortion ratio (percentage of pregnancies aborted) than Hispanic women, whose abortion ratio in turn is higher than that of non-Hispanic whites. Since blacks vote Democratic in far greater proportions than Hispanics, and whites are more Republican than Hispanics or blacks, ethnic disparities in abortion ratios would be sufficient to give the GOP a significant boost--surely enough to account for George W. Bush's razor-thin Florida victory in 2000.
Well, it's definitely not a statement of fact that 40 million legal abortions caused there to be 40 million fewer babies born. What Taranto fails to understand is that legalizing abortion vastly increased the number of unwanted pregnancies, just as it also increased the sexually transmitted disease rate, by making unprotected coitus seem less risky. As U. of Chicago economist Steven D. Levitt notes in his bestseller Freakonomics, after the Roe decision in 1973, “Conceptions rose by nearly 30 percent, but births actually fell by 6 percent …” So, net, for every six fetuses aborted in the 1970s, five would never have been conceived except for Roe!
To paraphrase Homer Simpson, legal abortion turned out to be not just the solution to, but also the cause of, many unwanted pregnancies.
So, let's do the math, because Taranto sure hasn't. If that ratio held true overall (and I'm not sure that it does), then legalized abortion reduced the total number of births by 7 million, not 40 million. Most of the abortees would have been under 18, so that leaves about 3 million eligible voters. Their voting rate, being young and fairly minority would be low, so figure about only 1 million would have voted in 2004. If they would have gone 2 to 1 for Kerry (and who knows what the real ratio would be), that means the Roe Effect increased Bush's margin by 0.333 million, or about one-tenth. So, the Roe Effect would probably not be trivial, but it's not very important either. And of course, any guesstimate of how these aborted young people would have voted is just a guess.
If anybody wants to take a more sophisticated crack at estimating the size of the Roe Effect, please let me know what you come up with.
This is not to say that things like fertility and marriage don't have a huge impact on hows states voted in the last two Presidential elections. In this century, Republicans win in states with a high degree of "affordable family formation." Democrats win where suburban land is scarce, housing prices are high, people (especially whites) get married late or not at all, and have few children. My summary article that explains the red-blue map is here. You can follow the links to my other, more detailed articles explaining the link between affordable family formation and voting Republican.
It's testimony to the lack of clear thinking in our public discourse on the effects of legal abortion that Taranto has been pushing his Roe Effect idea for a long time without anybody ever making clear to him the massive flaw in his logic.
(Or, possibly people have explained it to Taranto and he simply chooses to mislead people about the impact of abortion. That wouldn't be the first time anybody has chosen to mislead the public about abortion's effects! For example, you have to read Levitt's hugely hyped chapter in Freakonomics on how legalizing abortion supposedly cut crime very carefully to understand why his celebrated theory fails most obvious historical tests. The reason Levitt's crypto-eugenic logic didn't work, with the first cohort born after legalization going on the worst teen violence spree in recent American history, is the same reason as Taranto overestimates the importance of the Roe Effect: abortion drove up the number of pregnancies far more than it drove down the birthrate.)