Classed Choropleth Map

http://courses.washington.edu/info424/Labs/ChoroplethMap.html

A classed choropleth map differs from an unclassed map, in that intervals are created to display the data in a more simple manner. The number of intervals created can vary, as can the way data is divided up into intervals. Data can be divided into equal steps, natural breaks, or quantiles. The map above is an example of a classed choropleth map, and depicts a one-year forecast change in jobs for 2010 vs. 2009. The data has been divided into 6 intervals with a different color for each one.