A choropleth map uses colors or shading to show differences between areas. Areas that share a quality are colored or shaded alike.
Choropleth maps can be used to show differences in quantity also. If you wanted to show the percent of people graduating from high school on a world map, you could use ten colors to represent 0 to 10%, 11 to 20%, 21 to 30%, and so on.
Mapping information locates it for you. You know where it exists. And you have a starting point for finding out why it is there. ( info via http://ecedweb.unomaha.edu/lessons/feogzc.html)
DIRECTIONS FOR CREATING A CHOROPLETH MAP
1. Determine the mapping categories.
Subtract the lowest value from the highest value to calculate the range of the numbers.
Decide upon the number of mapping categories. Five to ten mapping categories are adequate for most maps.
Divide the range by the number of mapping categories to determine the numbers to include in each category.
2. Choose a color code or shading pattern for each category. The colors or patterns assigned should increase from light to dark to represent the lowest to highest category.
3. Locate and label each country on an outline map, determine its mapping category, and color or shade the country appropriately.
4. Title the map and add the key or legend to the map.