All Terrain Thinking

A Compendium of things I think are Important

Economics: It's not just whats' in your wallet

Bar and column graphs are most appropriate when we have non continuous variables-a good example being graphs of variables such as income or population growth for the nine census regions in the US. While New England and the Pacific regions make sense, there is no notion of continuity as we move from one region to another so we would not want to use a line graph. Below we have a bar graph of the distribution of US population by regions, the same information as displayed in the pie graph-just a different spin. In both graphs we would see that the two largest regions are the East North Central and the South Atlantic, each with populations over 40 million.

We could go beyond this to look at the stack graphs which convey information that would normally appear in a bar/column graph and a pie graph. Below are two stack graphs. In the first, the height of the columns provides us information on total US population in 1900, 1950, 1980, and 1990, while the division of the coulmn allows us to guestimate the regional population figures. What is not that easy to see here is what has happened to the share of population in a region. For example, what has happened to the share of the US population in the Pacific region between 1900 and 1990. This information can be found in the second graph, but this additional information comes at a cost-we lose the ability to tell anything about the population. As you know from your Economics, there is no free lunch.

 

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