Compare methods

	Choropleth Classification	Cartogram Construction
Field	Human Geography	Human Geography
Family	Process / pipeline	Process / pipeline
Year of origin	1967	2004
Originator	Thematic cartography tradition (class-interval methods synthesized by Slocum et al.; Jenks's optimal method)	Cartogram tradition (diffusion method by Gastner & Newman; circular method by Dorling)
Type	Procedure for grouping data values into ordered classes for a choropleth map	Map transformation that rescales region area to represent a variable
Seminal source	Slocum, T. A., McMaster, R. B., Kessler, F. C., & Howard, H. H. (2009). Thematic Cartography and Geovisualization (3rd ed.). Pearson Prentice Hall, Upper Saddle River, NJ. ISBN: 9780132298346	Gastner, M. T., & Newman, M. E. J. (2004). Diffusion-based method for producing density-equalizing maps. Proceedings of the National Academy of Sciences, 101(20), 7499–7504.
Aliases	Class Interval Selection, Data Classification for Maps, Choropleth Class Breaks, Thematic Map Classification	Value-by-Area Map, Area Cartogram, Density-Equalizing Map, Anamorphic Map
Related	4	4
Summary	Choropleth classification is the cartographic procedure of grouping the values of a quantitative variable into a small number of ordered classes so that areas can be shaded on a thematic map. Because a continuous distribution must be reduced to a handful of colour categories, the choice of how many classes to use and where to place the break values strongly shapes the map's message — the same data can look uniform or sharply divided depending on the scheme. Standard methods include equal interval, quantile, Jenks natural breaks, standard deviation, and head/tail breaks, each making different assumptions about what pattern the map should reveal.	A cartogram is a map in which the area of each region is rescaled so that it is proportional to some variable — population, votes, GDP — rather than to its true geographic size. The aim is to correct the visual bias of ordinary maps, where large but sparsely populated regions dominate the eye while small, populous ones nearly vanish, by making each region as big as the quantity it represents. Cartogram construction is the family of techniques that produce these value-by-area maps, ranging from contiguous density-equalizing diffusion to non-contiguous circle and rectangle methods, each balancing the accuracy of areas against the recognizability of shapes.