Erik W. alerted me to this CNN map that shows FBI statistics about safety of American cities. As Eric pointed out, this is prototypical of chartjunk a la Tufte. A lot of ink is used to depict 12 points of data (top 3 cities in safety, crime, improvement and decline).
Imagine the reader trying to find the 3rd most improved city. She either has to find all the blue dots and then figure out which is #3; or she needs to find all the #3 dots and figure out which is blue. As they say, it's "hard work". In fact, finding the dots among the forest of large text is hard work by itself!
How would I re-make this chart?
- Highlight only the states containing data (California, Michigan, Missouri, Ohio, Georgia, New Jersey, New York); gray out all other states and their boundaries
- Separate the states from the cities; only write the State name once for each State; reduce the font size
- Instead of dots, use numbers. So the most dangerous city (St Louis) gets a red "1", Oakland gets a purple "3", etc.
- Remove Mexico, Canada and water from the map
The map gives the false impression that crime is relevant only along the coasts and the lakes, when in fact, the map is just saying that most cities in the U.S. are located along the coasts and the lakes. Using such a map to depict city-level statistics creates distortion because cities are not evenly distributed across America.
Beyond that, what is the point of this map? Is it merely a geography class telling us where each city is located? How is it better than a simple table listing the cities in order?
Reference: "U.S. City Safety Rankings", CNN, 2006.