Univariate Choropleth Map

Univariate choropleth maps are thematic maps that display only a single variable, such as population density or landownership. In this case, the map shows the percentage of Americans living in poverty in different rural counties across the country. The trend in this map seems to be that counties lying in the North have lower poverty rates than in the South.

http://www.dailyyonder.com/files/images/2008PovertyCountiesMapfour.jpg