Univariate choropleth map

http://www.google.com/imgres?imgurl=https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFasPDDMXL3z8B9Ho6S8fG3reeGri1MojNWhc_JnbVECUB2RIngJ7J3HnGXHb6J1CfWnQr4PmxDLDas_0w-t4vH5Vx0iEeNogIGt6HPi7-UIsE-PM5c5F2bxNT5AGQEZWuSjOMdLuz2-c/s400/Choropleth.gif&imgrefurl=http://mapcollection2009.blogspot.com/&usg=__Q7Q5sw8SMfZUKz9WhCYR66VJa4c=&h=250&w=400&sz=131&hl=en&start=12&zoom=1&um=1&itbs=1&tbnid=mL6h22I7MgpoVM:&tbnh=78&tbnw=124&prev=/images%3Fq%3DUnivariate%2Bchoropleth%2Bmap%26um%3D1%26hl%3Den%26sa%3DN%26tbs%3Disch:1
This is an univariate choropleth map of the United States which displays water usage throughout the country. An univariate choropleth map displays only on set of data as can be seen in this particular map.