Choropleth Map

The choropleth map is based on predefined areal units, such as states, counties, census tracts, etc. Areas are shaded or patterned in proportion to the measurement of the statistical variable being displayed on the map, such as population density or per capita income. Above is an example of a choropleth map created on the U.S. Bureau of the Census it reveals the number of males per one hundred females in the year 2000.