Display of a measurement and 'size'
Direct shading of regions on a map can only display the values of one measurement. It is possible to display the value of this measurement and also a different 'size' measurement for the region if they are represented by coloured circles on the map. The circle's colour again represents the main measurement and its area is proportional to the 'size' of the region.
Circle area should be proportional to size, not circle diameter.
The 'size' measurement that is represented by circle area is often population, but it can be more closely associated with the main measurement. An example is shown below.
AIDS/HIV in Africa
The circles on the map below describe the incidence of AIDS/HIV in African countries in 2005. The area of each circle represents the total number of cases in that country. The colour describes the percentage of the population with the disease.
Click on any country to see its AIDS/HIV incidence numerically.
Increasing the size of the circles a little (using the slider) makes the information stand out better.