What would a minimal example for a choropleth map in Mathematica look like?

Question

What would a minimal example for a choropleth map in Mathematica look like?

I can read in a ESRI Shapefile using Import, but do not know how to work with th

Answer 1

Graphics[
   {
    ColorData["ThermometerColors"][
                            Rescale[CountryData[#, "GDPPerCapita"], {100, 50000}]
                                  ] /. HoldPattern[Blend[___]] -> Yellow, 
    CountryData[#, "Polygon"]
   } & /@
   CountryData[]
]

And why the replacement? If there are no data of the required type for a given country CountryData returns Missing["NotAvailable"], causing ColorData, and its underlying Blend function not to return a specific RGB value. I replace this unevaluated Blend with the color Yellow.