Purple maps of the 2012 presidential election

From Bob Vanderbei:

As I’ve discussed with respect to other maps, I prefer the bidirectional color scheme (that is, I prefer the colors in Bob’s bottom map, which meet in the middle at white (actually, I’d use light gray) to the unidirectional scheme in his top map).

Either way, though, the maps show a lot. The second map, in particular, shows the general (but not complete) pattern of uniform partisan swing. These are simple but very effective displays.

8 Responses to Purple maps of the 2012 presidential election

  1. PQuincy November 8, 2012 at 8:08 am #

    It shows a lot…but also conceals a lot because it rests on geographic territory, not population (which, for voting, is what matters). It would be a lot of work, I guess — though mapping technologies are getting amazing — but a population weighted county map with either color scheme would be far more useful than either of these examples.

    • Andrew Gelman November 8, 2012 at 8:27 am #


      Your idea of a map could be useful too . . . but instead of saying it would be “far more useful,” I think it would be better to say that your map could be useful also. In making graphs, we have to get away from the idea of thinking we can make one best perfect graph. Instead, let’s accept that, in many settings, multiple graphs will be needed to tell our story.

      • Paul Crowley November 8, 2012 at 9:19 am #

        No graph is perfect, but if I had this and the equivalent cartogram, I wouldn’t spend a moment looking at this.

        • Andrew Gelman November 8, 2012 at 10:26 am #

          I like the above maps because I can look at them right away and identify where things are happening.

          • Bill November 8, 2012 at 3:35 pm #

            I agree with Andrew. In the second map, I’m most interested in knowing which areas show the most “reddening” since 2008. The map as presented makes it easy to figure out that the changed areas are concentrated around West Virginia, Indiana, and Utah. Most readers would have trouble identifying these states in a cartogram.

  2. K November 8, 2012 at 7:19 pm #

    I made such a map for the 2004 election; I used lightness of color to show population of county. It was actually very revealing. While counties with major cities were very blue and very populous, surrounding counties were reddish and significantly populated. It shows how the dense blue cities are balanced by their semi-dense reddish surrounding suburbs. I don’t have one for 2012, and the method I used was fairly crude (overlay one map on top of another), but one could conceivably tap into census data on population at county level to get that value.

  3. Noumenon November 8, 2012 at 10:46 pm #

    Why is the lower Mississippi so blue?

  4. Stan Wilson November 9, 2012 at 1:53 am #

    Well…will ya look at Texas.