Scaling to radius or area?

A collection of common dataviz caveats by

A usual practice in data visualization consists of scaling a graphic component to a numeric value. For instance, bar lengths are scaled to values in a barplot. When the value is scaled to an area, scaling it by two sides at the same time produces a quadratic effect for a linear change. This amplifies the differences.


Here is an example coming from the Barack Obama’s State of the Union speech in 2011. It shows the 2010 Gross Domestic Product of 5 countries, each value being represented by a circle. The radius of each circle has been scaled based on the size of each nation’s economy.