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FiveThirtyEight

Politics

Shortly after the county-level election results became available, we started seeing maps like this:

From a quick look at this graph, it appears there’s something special going on with these white people in Appalachia who didn’t want to vote for Obama.

The actual picture for white people, as I estimate it, is slightly different. The complicating factor is that, at the same time that whites in some areas were moving toward McCain, blacks everywhere were moving toward Obama. Maps of the total vote show the sum of the two patterns.

If there’s a question about what whites in particular are doing, we can try to separate out their votes. To estimate Obama’s vote share among nonblacks within each county, we used the following calculation:

Obama got 96% of the black vote. If he got 96% in every county, which cannot be far from the truth, simple algebra will show his share of the non-black vote in every county. If B is the proportion black in the county and X is the (unknown) Obama vote share among non-blacks, then, for each county:

Obama’s vote share = 0.96*B + X*(1-B).

And so, under these assumptions,

X = (Obama’s vote share – 0.96*B) / (1 – B).

Here’s the map of Obama’s estimated vote share among non-blacks, by county:

The Appalachian counties don’t stand out in this map. McCain did extremely well among whites in a much broader area in the southeast, with the Applachian counties standing out in the earlier map only because they had very few black votes to cancel out the swing among the whites. Actually it looks like McCain did even better in some of the counties just south of that Appalachian belt.

P.S. Thanks to Ben Lauderdale and Yu-Sung Su for the maps.

P.P.S. It wouldn’t be so easy to estimate Kerry’s vote share among nonblacks in 2004. Kerry got only 88% of the black vote and so it’s less reasonable to approximate his vote share as being constant across counties.

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