Last month Lisa Charlotte Rost published a post on Datawrapper’s blog full of tips about choropleth maps: when to use them (and when not to), how to make them better (lots about colour use), along with some examples of good ones. Worth bookmarking.
She followed that up with another post focusing on one particular factor: the size of the geographic unit. Choropleth maps that shows data by municipality, county, region, state or country will look quite different, even if they show the same data. Averages tend to cancel out extremes. She gives the following examples: