Hibbs writes:

The 3rd quarter data posted by the BEA yesterday are so dire that I [Hibbs] changed my tune and generated a new forecast based on the latest data.

October 31, 2008 update of Presidential Vote Forecast: Preliminary estimates of 2008q3 national income data released on October 30 by the BEA indicate that the economy has weakened so much that I have updated my 2008 election forecast: The Bread and Peace model now predicts a 2-party vote share for McCain of 46.25%, implying Obama will win by a margin of 7.5 percentage points.

Just as a reminder, here’s the graph of Hibbs’s model applied to earlier elections:

As you can see, the incumbent party sometimes loses but they never have gotten really slaughtered. In periods of low economic growth, the incumbent party can lose, but a 53-47 margin would be typical; you wouldn’t expect the challenger to get much more than that. Such things can happen (see, for example, Eisenhower’s performance against Stevenson in 1952) but it wouldn’t be expected.

Len Adleman and Mark Schilling sent along this paper in which they found systematic differences in results from different pollsters:

We compared polls produced by major television networks with those produced by Gallup and Rasmussen. We found that, taken as a whole, polls produced by the networks were significantly to the left of those produced by Gallup and Rasmussen.

We used the available data to provide a tentative ordering of the major television networks’ polls from right to left. Our order (right to left) was: FOX, CNN, NBC (which partners with the Wall Street Journal), ABC (which partners with the Washington Post), CBS (which partners with the New York Times). These results appear to comport well with the commonly held informal perceptions of the political leanings of these agencies.

I guess this makes sense, given that these different news outlets want to make their readers happy. It still surprises me a bit–I thought all these pollsters were pros. It’s not that polling and poll adjustment are easy or automatic–a lot of subjective decisions still need to be made–but I’d think it would be possible to do this without being influenced by your political predilections or those of your audience.

P.S. Some quick comments on the presentation of the results:
- I’d combine tables 2 and 3, and tables 4 and 5.
- I’d remove the second decimal place in Tables 6, 7, 9. Anything less than 0.1 percentage point is both unmeasurable (realistically speaking) and unimportant.
- I’d recommend doing all comparisons relative to the avg of all polls rather than relative to Gallup or Rasmussen. It’s clearer to have a single comparison.
- The x-axis in Figures 2 and 3 are hard to read.
- Table 10 would be clearer as a time-series graph.

Regarding the probability-of-a-decisive-vote calculation, I’ve received several comments along these lines:

Given the virtual certainty that there would be a recount in a decisive state where the election was very close (not to mention decided by a single vote), and given the virtual certainly that the recount would not yield a second identical result, wouldn’t the true probability that one’s vote would make a difference in both the original count and the recount be many times larger than your estimates? I’m not sure how to calculate that higher probability — but I suspect it would range between 2 X and X-squared where X is the Gelman probability that your vote would be decisive.

My reply: No, that’s not right. See footnote 6 of the article, which points you to p.674 of my BJPS paper with Katz and Bafumi which addresses this issue. The key is that, at some point, the election is determined, and each vote slightly changes the probability of McCain or Obama is winning. Before the election, the exact vote margin is uncertain, and the probability that your vote is decisive must be calculated by averaging over all possible vote margins that might occur. The result is that our calculation works out.

From a recent email interview:

- Why the polls don’t matter while the elections are ‘predictable’? Is there too much confidence in a supposely ‘Obama landslide’?

Based on the economy, Obama was predicted to get something like 53% of the two-party vote.  Due to the U.S. electoral system, if you win 53%, you will win many many states and so the Electoral College will look more like a landslide.

- Do you give any credit to this Bradley Effect?

My guess is that this pattern is less of an issue in a highly contested national election.

- Your book ends with the myth that the rich elite votes Democrat and the poor vote Republican, but does it mean that American politics are in a way a battle of elites (those in the poorest and those in the wealthiest States)?

Yes, U.S. politics is in many ways a battle of elites:  the liberal elites in the Northeast, West Coast, and Upper Midwest, versus the conservative elites in the South and the rest of the country.

- If the image of the poor, religious, gun-loving Republican is a myth, why Republicans keep using the ‘real America’ theme and talk about values of small towns in the middle of the poorest part of the country? Is more a battle of rural vs. urban?

I am not sure here, but I suspect that rural images are popular even with many Americans who live in cities and suburbs.

- And what exactly makes the upper middle class in the wealthier States vote Democrats while their peers vote Republican in other States?

The upper middle class in wealthier states are more likely to be socially liberal (even if they are economically conservative).  In poorer states, the upper middle class tends to be both economically and socially conservative.

- Why the economic slowdown benefits Democrats? Do the richest not share the view that Democrats can handle better economic issues, as the polls generally show, or do they vote against their economic interests? (sort of the opposite that What’s the Matter with Kansas said)

A bad economy makes the current administration less popular among all groups.

- Are race or inmigration the main diving lines? And if so isn’t gonna affect disproportionatelly the Obama result?

Race is a big dividing line, but the line is already there.  At this point, people of all races are reacting to the positions of the candidates and new information.

- I was intrigued by your argument that religion matters nearly as much in European election than in American ones. How could it be when here religion is out of the political campaigns and discourse and there is no question whatsoever about the faith of candidates?

I’m not sure why it’s happened, but the two parties in the U.S. differ much more on social issues than they used to.

- I’d really appreciate your comments. Actually, I liked What’s the Matter with Kansas, but I always felt there was something wrong with the picture, as in Europe the richest tend to be more conservative (althought I also attributed to the fact that, in Europe, Democrats will be probably center-right and Republicans far on the right…). Anyway, thanks to you and your book for the clarification!

I hope this is helpful to you and your readers.  I liked “What’s the Matter with Kansas” also.  That book doesn’t claim to be a statistical analysis.  What it has is analysis of the rhetoric of the Republican party and lots of discussion of the battles within different Republican factions in Kansas.  It’s important stuff.  I think that quantitative studies such as ours and qualitative studies such as Frank’s are both important.

Here’s the article by Aaron, Noah, and myself on a topic we’ve discussed more formally before: why it makes sense, when voting, to consider the election outcome as it affects the country as a whole rather than just its effects on yourself.

Just in case you stumbled upon this blog by accident . . .

Yair made the graphs. See here for his explanation.

How is the 2008 election different from 2004, beyond the (currently predicted) national swing of about 4 percentage points (enough to move from Kerry’s 49% of the vote to 53% for Obama)?

When I spoke yesterday, someone asked about the changes in the electoral map since 2004 and what did it all mean, are the red states being painted blue etc?  My quick answer is that the relative positions of the 50 states aren’t changing much, it’s the whole country that’s shifting.  This was my impression based on looking at the map and also based on generally seeing uniform partisan swing in votes and attitudes.

But what do the data say? Here’s a graph of Obama’s predicted share of the two-party vote in each state (based on Nate Silver’s recent poll aggregation) compared to Kerry’s in 2004:

I then fit a simple linear regression; here’s a map of the residuals, showing where Obama is doing particularly well or poorly, compared to last time:

I used regression residuals rather than simply plotting or map the differences because of “regression to the mean”: the predictable pattern that the Democratic vote will go down (relatively speaking) in places where they did particularly well last year, and go up where they did particularly poorly. Instead, the regression residuals show changes that are unexpected (relative to the linear model, that is; of course it’s not unexpected that McCain is doing relatively well in Arizona, but the simple linear regression of 2008 on 2004 doesn’t know about home states).

2000/2004

How big are these changes? One way to calibrate is to look at changes from 2000 to 2004. These will be close to the smallest changes we’ll ever see, since 2004 was really a replay of the 2000 election. Here’s the scatterplot:

And here’s the map of residuals:

So, the relative changes of states in 2008 seem greater than the changes in 2004. On the other hand, the 2008 estimates are based on fallible poll data; maybe the election outcomes will be less variable.

Nate Silver, Aaron Edlin, and I estimated the probability that a single vote in any state will be decisive in the presidential election. It was Aaron’s idea, Nate supplied the simulations, and I calculated the probabilities and made the graphs.
Here’s our article describing what we did, here’s the abstract:

One of the motivations for voting is that one vote can make a difference. In a presidential election, the probability that your vote is decisive is equal to the probability that your state is necessary for an electoral college win, times the probability the vote in your state is tied in that event. We compute these probabilities for each state in the 2008 presidential election, using state-by-state election forecasts based on the latest polls. The states where a single vote is most likely to matter are New Mexico, Virginia, New Hampshire, and Colorado, where your vote has an approximate 1 in 10 million chance of determining the national election outcome. On average, a voter in America has a 1 in 60 million chance of being decisive in the presidential election.

and here are some graphs:

There are more graphs if you follow the link to the article.

As Aaron, Noah, and I have discussed, it can be rational to vote even when the probability of decisive vote is 1 in 10 million.

P.S. Typo in Figure 1 caption above fixed.

P.P.S. See here for more discussion of why we can compute the probability of a decisive vote, even though the election might be decided by a recount

The New America Foundation in D.C. on Monday at noon.

The University of Chicago statistics department Tuesday at 4:30.

Sometimes you hear discussion of how the red states get more from the government than they pay in taxes while the blue states get less and pay more.  This is slightly misleading because the blue states are richer and rich people pay a higher rate of income tax, but it does raise the interesting question of the national effects of the graduated income tax.

For some perspective on where this is coming from, here’s a fun bit from chapter 9 of our book:

In our office is a map from 1924 titled “Good Roads Everywhere” that shows a proposed system of highways spanning the country, “to be built and forever maintained by the United States Government.” The map, made by the National Highways Association, also includes the following explanation for the proposed funding system:  “Such a system of National Highways will be paid for out of general taxation.  The 9 rich densely populated northeastern States will pay over 50 per cent of the cost. They can afford to, as they will gain the most.  Over 40 per cent will be paid for by the great wealthy cities of the Nation. . . . The farming regions of the West, Mississippi Valley, Southwest and South will pay less than 10 per cent of the cost and get 90 per cent of the mileage.” Beyond its quaint slogans (“A paved United States in our day”) and ideas that time has passed by (“Highway airports”), the map gives a sense of the potential for federal taxing and spending to transfer money between states and regions.

I’ll see if I can get someone to take a picture of this amazing map so I can post it on the blog.