Choropleth Counties  Choosing how to display data is often the
most difficult part of the data visualization process. Would a
bar chart be superior to a pie? Perhaps a scatter would tell
more than two bar charts? One of the most difficult of these
choices is between filled maps (choropleth) and shapes.
Choropleth maps have several advantages. First, they avoid
overlap and because of it they are usually very neat and
beautiful. Choropleth maps also tend to make it easy to spot
trends geographically, like the clusters of major cities in the
household income map above.  However, shapes also have some
interesting traits. First of all, it can be much easier to spot
small outliers. You may notice how Los Alamos County, NM stands
out in the bottom view, but is nearly invisible in the top view.
Shapes also have the relative advantage of not distorting by
size, because they give equal weight to each mark. This can be
frustrating though, since they can overlap, as in the eastern US
with this map.  Regardless of your c