Cons:
– Since the choropleth map uses an average number to represent defined areas, the viewer can not gain detailed information or perspective on any area’s internal conditions. This can be solved by making the map interactive (like “The Geography of Government Benefits” from The New York Times)
– The areas are not uniform: equating the visual importance of each county with its geographic area rather than with the number of people living in there, giving sparsely populated areas great visual emphasis. This can be solved by using the method of mesh/grid-square mapping (dividing the map into equal sized units/squares and then color each one according to the data being encoded). An example of a mesh map (the grid squares are 1km on a side) :