Physicist Dirk Brockman used data on dollar bill movements to identify economic regions.
While the physical transfer of cash may no longer represent our economic activity as well as it once did, it is still interesting stuff. I do quibble with the concept that the economic activity regions correspond to “states” (Brockman is German). I also think information on direction of flow is extremely important. I am happy to see that the concept of “The Carolinas” is apparently real and that Ohio State fans express their dislike of Michigan with their wallets too.
*Hat tip to Jennifer Ouellette.