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Net flow of households across US regions

These are a set of diagrams taken from a recent WSJ article talking about how, “the pandemic changed where Americans live.” I know that this is a topic that gets a lot of air time (both here on the blog and elsewhere), but these diagrams do a good job of showing the flow of people, as well as how things may have changed/accelerated since 2018.

These diagrams also remind me of the work of Charles Joseph Minard. A French civil engineer, Minard is best known for his contributions to the field of information graphics, and in particular his flow maps. His most famous piece of work — which I happen to have hanging at home — is his depiction of Napoleon’s losses during the Russian campaign of 1812.

The map itself is from 1869 and is packed full of information. It shows the number of Napoleonic troops as they left for Moscow, the distance they traveled, the outside temperature (the French weren’t properly prepared for the cold), latitude and longitude, the direction of travel, and the location of the troops relative to specific dates.

The point of the diagram was really to show how disastrous this campaign was for Napoleon. The thick beige band on the left is showing over 400,000 troops setting out. But by the time they reached Moscow — which, by the way, had been abandoned before their arrival — only about 100,000 troops were left.

The thin black bar on the bottom is showing how many troops ultimately remained and returned at the end of the campaign — the number was only about 10,000. So the vast majority of Napoleon’s troops perished. Supposedly over half either starved or froze to death.

Some 150 years later, and we are still using flow charts to clearly depict the movement of people and things.

1 Comment so far

  1. Paul Ching Lee

    I’m a transportation planner/engineer and the map of Minard blew me away. I’ll try my best to get my hands on one of his flow diagrams. Thanks for pointing the way.
    Paul C. Lee, PEng.


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