Cartograms and Map Distortions
Further to my earlier post on proportional election maps, Science News had an article last month about the art of map distortion in general. Using the example of using a map to show the incidence of a particular disease, the article argues that
Such representations … can be misleading. Inevitably, cities would show a higher incidence than rural areas merely because the former have larger populations. Plotting per capita incidence takes care of that problem but discards information about where most of the cases occurred.
One solution is to take out variations in population density but still show how many cases occur in each region. This can be done on a distorted map in which the sizes of geographic regions appear in proportion to their populations, whether it’s people or goods, or other items. Such a map is known as a cartogram.
The article goes on to describe some of the challenges and techniques involved in “transforming” a map into a cartogram. Interesting reading, if a bit overwhelming.