  Cartograms are maps in which areas of geographic regions (countries, states)
appear in proportion to some variable of interest (population, income).
Cartograms are popular visualizations for geo-referenced data that have been
around for over a century. Newspapers, magazines, textbooks, blogs, and
presentations frequently employ cartograms to show voting results, popularity,
and in general, geographic patterns. Despite the popularity of cartograms and
the large number of cartogram variants, there are very few studies evaluating
the effectiveness of cartograms in conveying information. In order to design
cartograms as a useful visualization tool and to be able to compare the
effectiveness of cartograms generated by different methods, we need to study
the nature of information conveyed and the specific tasks that can be performed
on cartograms. In this paper we consider a set of cartogram visualization
tasks, based on standard taxonomies from cartography and information
visualization. We then propose a cartogram task taxonomy that can be used to
organize not only the tasks considered here but also other tasks that might be
added later.
