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Monday, November 06, 2006

Why I Never Believe Polls

Based on the most current polls, the Democrats are almost surely going to take control of the House, and have a decent shot at the Senate as well.

I'm not going to make any predictions how I think it will play out in the hand, but if the Dems to take the House, I'm not going to sit shiva. But if they take the Senate, ouch.

But I don't trust polls, and I wouldn't be completely shocked if the GOP manages to hang on to the House.

The problem with polls is that what people say and what they do are often quite different. As long as polls are administered by human beings, people's answers are going to be affected by that. Often people will give the answer that they think the pollster wants to hear.

The classic, oft-cited example is the 1989 New York mayoral election between Rudy Giuliani (white) and David Dinkens (black). Before the election, polls showed Dinkens trashing Guiliani, but in the end Dinkens won by only a couple of points. In the book Freakonomics, Steven Levitt writes that people told pollsters that they were going to vote for Dinkins because they wanted to appear to be more color-blind that they actually are.

Another example Levitt gives is David Duke's Senate run in 1990. Duke did significantly better in the election than in the earlier polls. Who is going to admit to a pollster that they are going to vote for a KKK Grand Wizard?

I believe the same is true today. It's cool to bash Republicans. They're on the defensive. It seems like the politically correct thing to say to a pollster is that you're going to vote for the Democrats. But when no one is looking, and no one knows, plenty of people who said they would vote one way will actually vote other way.


It's not just that. I wrote about this a couple of weeks ago - people who generally swing left are more likely to be called by pollsters and more likely to answer.

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