<P> A cartogram is a map in which some thematic mapping variable--such as travel time, population, or GNP--is substituted for land area or distance . The geometry or space of the map is distorted, sometimes extremely, in order to convey the information of this alternate variable . They are primarily used to display emphasis and for analysis as nomographs . </P> <P> Two common types of cartograms are area and distance cartograms . Cartograms have a fairly long history, with examples from the mid-1800s . </P>

What types of data are best measured by a cartogram map