November 5th, 2008, by Andrew
After a quick look at the election results and exit polls (from www.cnn.com), some thoughts:
1. The election was pretty close. Obama won by about 5% of the vote, consistent with the latest polls and consistent with his forecast vote based on forecasts based on the economy.
2. As with previous Republican candidates, McCain did better among the rich than the poor:
But the pattern has changed among the highest-income categories:
3. The gap between young and old has increased–a lot:
But there was no massive turnout among young voters. According to the exit polls, 18% of the voters this time were under 30, as compared to 17% of voters in 2004. (By comparison, 22% of voting-age Americans are under 30.)
4. By ethnicity: Barack Obama won 96% of African Americans, 68% of Latinos, 64% of Asians, and 44% of whites. In 2004, Kerry won 89% of African Americans, 55% of Latinos, 56% of Asians, and 41% of whites. So Obama gained the most among ethnic minorities.
5. The red/blue map was not redrawn; it was more of a national partisan swing. See this state-by-state scatterplot of Obama vote in 2008 vs. Kerry vote in 2004:
The standard deviation of the state swings (excluding D.C. and the unusual case of Hawaii) was 3.3%. That is, after accounting for the national swing in Obama’s favor, most of the states were within 3% of where they were, compared to their relative positions in 2004.
By comparison, here’s the 2000/2004 graph:
The standard deviation of these state swings was 2.4%. This was even less variation–2004 was basically a replay of 2000–still, the relative state swings of 3.3% in 2008 were not large by historical standards.
Again, Obama didn’t redraw the map; he shifted the map over in his favor. (Or, to put it more precisely, the economy shifted the map over in the Democrats’ favor and Obama took advantage of this.)
Here’s the map showing where Obama and McCain did better or worse than expected based on 2004:
6. Finally, how did the pre-election polls do? Unsurprisingly, they pretty much nailed the national vote. And what about the relative positions of the states? The pre-election polls did well there too, at least using Nate Silver’s aggregations. Here’s the scatterplot:
Pretty damn good. The standard deviation of the discrepancies, again excluding D.C. and Hawaii, is 2.5%, which is a big improvement on the 3.3% using Kerry04 alone.
I see some systematic patterns: Obama underperformed where the polls had him way down, and he outperformed where the polls had him up. We should go back and look at these patterns from earlier elections and see if this is consistent. If so, it suggests a way to improve forecasts for next time.
P.S. Age graph fixed from first posting; thanks to Andy Guess for pointing out the error.
- Predicting the election outcome months ahead of time: discussion and link to revised paper with Kari Lock
- Bayesian Combination of State Polls and Election Forecasts
- No beef with AK or HI
- Did Race Win the Election for Obama?
- Does America remain a center-right nation?
Entry Filed under: Elections