A statistical map with bar charts

Reproduced from Cleveland, W.S. & Mcgill, R. 1984. Graphical Perception - Theory, Experimentation, and Application to the Development of Graphical Methods. Journal of the American Statistical Association, 79, (387) 531-554.

Framed rectangle charts (bar charts) have been encoded on to the different geographical regions on the statistical map above. It illustrates the geographical variations of certain events such as prevalence. This representation may reduce the time required to extract the information and also may reduce error in judging the magnitude of the values (see Cleveland 1984).