Univariate Choropleth Map

http://www.dailyyonder.com/poverty-rate-jumps-rural-america/2009/11/23/2466

Univariate choropleth maps, like the title suggests, only displays a single set of data. This maps data set is poverty in rural America in 2008. The highest poverty percentage is represented by red and then fades toward the average, and the lower percentage starts at a pale green and progresses to a dark green color. The trend in this map is that counties with higher rates of poverty tend to be in the south and northwest, and counties with lower rates of poverty tend to be in the north.