Geographical spaces aren’t uniform so some areas may appear overrepresented.The visual tends to generalize the data.They clearly display densities (ratios) of quantities using color. One way to normalize the choropleth map is to divide the statistical values with the population of the geographic area. Make sure to normalize the attribute for the choropleth map (otherwise, the visual is misleading). For example, large geographic areas (like Texas or California) might dominate the visual. One particular drawback of using choropleth maps is that geographical spaces aren’t uniform, and thus the displayed results might not portray the right results. However, choropleth maps have some limitations.
We use choropleth maps to convey statistical values in different geographical scales, from local to global. As you can see, choropleths are good at displaying densities using colors. For example, let’s look at the unemployment rate by U.S.
With this type of thematic map, we use color to represent statistics proportionally to its location. The choropleth map is one of the most frequently used maps in geospatial data.
