Choropleth map
Thematic map using color to show data by area.
Belg4mit · Public domain
A choropleth map is a type of statistical thematic map that uses pseudocolor to represent an aggregate summary of a geographic characteristic within predefined spatial enumeration units, such as population density or per-capita income. It is likely the most common type of thematic map because published statistical data is generally aggregated into well-known geographic units, making them relatively easy to create using GIS, spreadsheets, or other software tools.
- creator
- Baron Pierre Charles Dupin
- term_coiner
- John Kirtland Wright
- common_usage_by
- 1940s
- type
- statistical thematic map
Lore & Background
More 'cartes teintées' ('tinted maps') were soon produced in France to visualize other 'moral statistics' on education, disease, crime, and living conditions.
Reader's Guide
Choropleth maps are significant because they provide an easy way to visualize how a variable varies across a geographic area or show the level of variability within a region. They bring together spatial data representing a partition of geographic space into distinct districts and statistical data representing a variable aggregated within each district. However, using pre-defined aggregation regions can result in issues such as the ecological fallacy and the modifiable areal unit problem (MAUP), because the constant color applied to each district masks variation within it. The choice of regions ultimately depends on the map's intended audience and purpose. For many variables, an isarithmic or chorochromatic map may be preferred, but in many cases the choropleth map is the only feasible option due to data availability.
Did You Know?
- Choropleth maps are distinct from heat maps or isarithmic maps, which use regions drawn according to the pattern of the variable.
Gallery
Frequently Asked Questions
What are Choropleth map's powers or role?
Its core ability is to paint entire enumeration units—counties, states, provinces—with a pseudocolor scale so readers can compare a single summary statistic across regions at a glance. Unlike point or flow maps, it never plots individual observations; it only conveys the aggregate number assigned to each predefined area.
How does Choropleth map's story end?
Choropleth map has no single ending because it remains one of the most frequently produced thematic map formats in use today. Its story continues in every GIS project, spreadsheet visualization, and news graphic that shades a region by a numeric value.
Why is Choropleth map important?
It is likely the most common type of thematic map because published statistics are already aggregated into well-known geographic units, making it straightforward to build with GIS, spreadsheets, or other tools. That simplicity and instant readability cemented its standard usage by the 1940s.
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