11
Mar
16

Shuffling Michigan

It’s election season here in the United States, and as we all know, the combination of democracy and mapping yields one main thing: cartograms! Those entertaining maps in which states, counties, or whatever have been resized based on their electoral significance.

The folks at Decision Desk HQ (decisiondeskhq.com) have been making cartograms for the party primaries, breaking each state out by county (or town, in some cases). I’ve only rarely seen county cartograms, and I don’t think I’ve seen one for election results before, so it’s great that they’re taking this on. But their approach is troubling.

Maps


2016 Republican primary results for Michigan. Decision Desk HQ on the left, New York Times on the right.

Their approach is to resize each county by population (# of total votes would be good, but no good could come of remaking these on the fly as votes come in), and try to keep the overall shape of the state. Unfortunately, in so doing, they shuffle the counties around any old which way. The Lower Peninsula of Michigan has 68 counties in reality, the Upper Peninsula has 15. But Decision Desk HQ has shoved most of the counties into the Upper Peninsula, which now has 58, vs. 25 that remain in the Lower Peninsula.

This means that we can’t really see spatial patterns, which is sort of the point of having a map. Notice how, on the NYT map, the gold-colored counties that went for Cruz are mostly clustered in the west. The Decision Desk HQ map keeps some of them there (in yellow), but scatters the rest of that cluster around the Upper Peninsula. The two purple counties both went for Kasich, and Decision Desk HQ would have us think they are neighbors (which would be an interesting thing to note as far as spatial patterns go), but in fact they’re the two teal-colored counties on the NYT map that are on opposite sides of the state. The list goes on.

A table would be better than the Decision Desk HQ map. Right now it misleads readers. If you don’t know Michigan Geography, you will come away with incorrect understandings of which regions of the state went for which candidates.

Making cartograms is hard. It is absolutely possible to level a charge of “spatial patterns are distorted” against almost any of them in some way. But most good cartograms at least try to preserve the topology. Example:

Does this mess up some of the spatial distribution? Most certainly. But the effort is there to try and keep some of it. Most states continue to border their real-life neighbors, and lie in approximately the correct direction to each other. The South is still in the south. Keeping those relationships, as best as one can, is critical. It’s what makes these things more valuable than an alphabetical table of states/counties/etc.

I must admit that I originally praised the Decision Desk HQ maps when I saw them:

PraiseTweet.png

That’s me. I said those things.

That’s because they do look pretty cool. And because I had no idea that all the towns of New Hampshire were probably in the wrong place. But when Michigan’s turn came around, I could not ignore the mangling of my beloved home state. I’m sorry, NH: I didn’t know what they did to you.

One Nice Thing: For those of you unfamiliar (since I post here only about every 2–3 years), I try to say one nice thing about any map I criticize. Decision Desk HQ deserves praise for applying cartograms to state election data; I’ve not seen that before (though perhaps others have done so). Constructing all these county/town population cartograms is no easy task. And they didn’t use the awful-looking Gastner-Newman algorithm. Instead, they’ve got a nice clean style of their own, which would be great if it were just much more accurate. I think that’s entirely possible to do while keeping to their aesthetic.


1 Response to “Shuffling Michigan”


  1. 1 dowlers
    11th March, 2016 at 6:13 pm

    Reminds me of http://xkcd.com/1653/ maybe they are big fans.


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