Cartograms: A Visualization Technique for Researchers

 

By Jeffrey Henning

As market researchers seek out better visualization techniques, it is worth investigating the cartogram. A cartogram is a map in which geographic entities (counties, states or countries) are resized according to any dimension of interest: population, sales, or – given that we are in election season – electoral votes.

When studying maps and charts, we recognize large areas as being more important. Which makes it confusing to see something like the 2008 U.S. electoral map below:

Source: Wikipedia, http://en.wikipedia.org/wiki/United_States_presidential_election,_2008

Visually it looks like John McCain (represented by the red states) won the presidential election. But while the red areas are visually larger, the blue states represent 68% of the votes in the Electoral College (365 votes) to the red state’s 32% (173 votes). That’s because the red states are more sparsely populated and electoral votes correlate to population (every state gets a minimum of 3 votes: 2 for its senators and then 1 for each representative, allocated by population).

Now contrast the above map to a cartogram, where the states have been resized to visually convey how many electoral votes they have:

Source: Colley Rankings, http://colleyrankings.com/election2008/

Here the greater electoral value of the 2008 blue states is discernible at a glance.

J. Richard Gott created this chart simply by drawing each state on graph paper with one square per electoral vote. In addition, he made sure that “all states which touch in reality touch on the map”. You can create cartograms as simply as that.

Alternatively, you can use specialty software to produce results that preserve more of the geographic features of individual states. Take this example:

Source: M. E. J. Newman, http://www-personal.umich.edu/~mejn/election/2008/stateelecredblue1024.png

How can you use cartograms in your work? To show locations, sales, market share or other attributes by state or country. For instance, here’s the number of locations by state for three major brands:

Source: Steph Abegg, http://www.stephabegg.com/home/projects/cartograms

To learn more about cartograms, check out:

• Worldmapper – The world as you’ve never seen it before
• Noncontiguous Area Cartograms
• Cart – Computer software for making cartograms
• Cartogram Generator