I’ve been reading William Playfair’s Commercial and Political Atlas, in which he invented the line chart. In the book, Playfair examines the imports and exports between Britain and various countries. To illustrate these trade relationships, Playfair created the first ever line charts that show the change in trade over time.
Each section of the book covered a different country, and each one contained a chart that showed the imports and exports like this:
I’ve been captivated by these charts and wanted to recreate them, but with modern data. You can find tons of US trade data at the US Census Bureau’s website, including a spreadsheet that has all the data in one place. I downloaded that data and put together a little application to create Playfair-esque charts.
The app displays all the countries that the US has trade data for, month by month going back as far as 1985. Each country is displayed in the list on the left with a sparkline chart of the trade data. A red fill indicates we are importing from a given country more than we are exporting, and a light green fill indicates we are exporting more than we are importing.
Exploring the data
The charts tell some really interesting stories. Some of the charts show a nearly identical relationship of imports to exports, both growing at the same rates, like these charts of the UK and Guatemala.
Or we can see what imposing sanctions on a country looks like, as illustrated by sanctions on Burma that were put into place in 2003:
Or what a coup in Haiti looks like:
Or what a massive tsunami can do to a place like the Maldives:
And one final one that I find very interesting, isn’t a country, but the import and export of what is classified as “Advanced Technology Products“, which includes things like biotech and advanced electronics products. Notice how up until the early 2000s we were exporting more of these products than we were importing, but by 2002 that balance shifted and the gap continues to increase:
I had fun creating this app, but one thing I didn’t expect was how much fun researching the charts was going to be. The charts that stuck out with trends that were abnormal all had interesting stories to tell about the history of the country.
In closing, I’ll end with a quote from Playfair in which he describes the concept of displaying numeric values in a line chart (remember, he was the first person to actually do this):
As the eye is the best judge of proportion, being able to estimate it with more quickness and accuracy than any other of our organs, it follows, that wherever relative quantities are in question … this mode of representing it is peculiarly applicable; it gives a simple, accurate, and permanent idea, by giving form and shape to a number of separate ideas, which are otherwise abstract and unconnected.
Well said, Mr. Playfair, well said. Your charts are just as effective nearly 200 years later.
- One of the first time-series line charts ever drawn was a visualization of the great American credit crisis (but probably not the credit crisis that comes immediately to mind). If you were to look at this chart today you might even mistake it for the charts of the housing credit…