Cartographers recommend that the choropleth mapping technique be used for thematic maps...?

Question

Cartographers recommend that the choropleth (graduated color) mapping technique be used for thematic maps of which kind of data?
A. Counts (e.g., net number of migrants per country)
B. Rates and Densities (e.g., migrants per 100,000 population)

Answer 1

B. Rates and Densities

Raw counts (option A) no not take into account that places with larger areas will often have more of whatever you're counting. If you're looking at a "per capita" or density type data, though, using choropleth mapping creates a more realistic image to see. Graduated color works well because it shows that the more pigment there is, that means the more of whatever it is is you're counting there is there.