Follow the Money

Did you ever wonder where your dollar bills go after you plop them down for your morning coffee? Well, it turns out George Washington, Ben Franklin and the other paper-money men are quite the jet-setters.

In February McCormick School of Engineering and Applied Science doctoral students Christian Thiemann and Daniel Grady (GMcC07) won the 2009 International Science and Engineering Visualization Challenge for their video that analyzes the ways people spend money — and therefore move — across the United States. The students used data from the web site Where's George?, which allows users to record a bill's serial number and then track its journeys as people spend it across the country.

Every time a dollar is spent in a new place means someone most likely moved it there, and Thiemann and Grady used this knowledge to show human travel patterns within the country.

They produced "Follow the Money: Human Mobility and Effective Communities" to animate the results. In the video tiny bills stretch from county to county on a map of the contiguous United States. Many bills from across the nation pass through big cities, such as Los Angeles. Smaller areas — such as Grady's home of Anderson County in Tennessee — have mostly short-range connections.

Grady and Thiemann are part of the research group of Dirk Brockmann, associate professor of engineering sciences and applied mathematics.