How Using Cartograms can make Election Maps Look More Representative of the Results

In many recent elections across the country, Democrats have tended to do better in the heavily-populated urban areas while Republicans tend to do better in the lightly-populated rural areas. Since the rural areas are clearly much larger in area than the urban areas, maps of these results usually show substantially more red than blue, even if the Democrat won the election overall. A good example of this is the 2012 Presidential election in Pennsylvania.

PA 12Pres results

There is clearly substantially more red than blue on this map. A person who may not be as knowledgeable of the political geography of Pennsylvania might look at this map and conclude that Pennsylvania voted strongly for the Republican. However, in actuality, it didn’t – Obama won Pennsylvania by a 52-47 margin in 2012.

So how could we alter the map of Pennsylvania to show that the Democratic cities have a larger impact on the results than the above map shows? One way to do this is to make a cartogram of the same election, and resize each municipality so that its size on the map is based on its population. If we were to do this, this is what we’d get:

PA 12Prez results resized by 10Pop

This map clearly shows the substantial impact that Pennsylvania’s Democratic cities have on the state’s election results. Both Philadelphia and Pittsburgh, as well as the smaller cities in the eastern part of the state (such as Harrisburg, Lancaster, Reading, Allentown, and Scranton) are dramatically expanded, thus showing their electoral impact more accurately. It’s pretty clear just by looking at this map that Obama won Pennsylvania in 2012, and even an untrained eye could look at this map and draw the correct conclusion.

Plus, I think this cartogram looks pretty cool.


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