Univariate Choropleth Map

 http://jsellers-maps.blogspot.com/2008_10_01_archive.html

Univariate Choropleth Maps only display a single variable or attribute on map. The example above is displaying the Acres of Hay harvested in 2002. The amounts are categorized by color shading the counties among the states in the US. Even though this is a univariate map, you can see by the increase in size of the county how the acres harvested increases as well. More land equals more hay harvested.