## November 02, 2008

### Vote.

The election is coming up very quickly, and just in time there is a statistical analysis of the likelihood that your vote will decide the election. [1] The analysis is due to Andrew Gelman and colleagues [2], and below is their main figure, showing which states are likely to be the closest races (lighter colors). For instance, my current home state of New Mexico (which was won by Gore by less than 500 or so votes in 2000, and won by Bush by less than 3000 votes or so in 2004 [3]) is one of the places where the national presidential election could come down to a single vote. This makes me especially glad that I got my vote in early (via absentee, since I'm in New York right now).

For those of you who haven't voted, but can, please make the rational choice [4] and vote in this election.

For those interested in the details, here's the abstract for Gelman's writeup [5]:

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.

(tip to Jake.)

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[1] For those who haven't yet discovered them, there are many places that are doing interesting kinds of forecasting for this election. fivethirtyeight.com is one that is frequently mentioned to me, which does sophisticated voting simulations.

[2] Gelman blogs the analysis at the Statistical Modeling, Causal Inference, and Social Science blog, and there's some additional commentary at Red State Blue State Rich State Poor State.

[3] These figures are, I think, roughly what I heard at a recent political rally, but they could be wrong either because of a bum memory or a biased source.

[4] Edlin, Gelman and Kaplan, "Voting as a Rational Choice: Why and How People Vote To Improve the Well-Being of Others." Rationality and Society 19, 293 (2007). Gelman has blogged some additional comments on this topic here.

[5] Gelman, Silver, and Edlin, "What is the probability your vote will make a difference?" Pre-print (2008).

posted November 2, 2008 03:03 PM in Political Wonk | permalink