I want to show the change in jobs and sales per state from 2006 to 2015.

Since I will be making a choropleth map, does this mean that I need to normalize the job and sales numbers before I make the map?

If so, what should I divide them by?


State area?


Are you sure you wish to use a choropleth map? It is probably the most overused and inappropriately used thematic mapping technique. It is ideally used to show ratio statistics where the size of the regions (states) are sized in proportion to the denominator of the ratio statistic. If the statistic is total something per unit area then go ahead and let each state be shown in its correct size and let the shade/intensity be proportional to the density statistic.

Your statistics are jobs and sales per state and you ask if you should divide values by population or area. Which statistics are most meaningful? I'm assuming you're interested in job rates and sales rates, per head or per thousand. If you really wish to use choropleths then you should adjust the sizes of each state to be proportional to its population. That is rather difficult to do.

An alternative is to use a conventional map of the states and place a symbol in each where the size of the symbol is in proportion to the state's population and the shade/intensity (or even height) of each is in proportion to the state's jobs/sales statistic. The type of thematic map is usually called proportional symbol and you have many variations upon which to choose: bar charts, pie charts, etc.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.