Scholars have long been interested in tracking “knowledge spillovers,” the way technical and intellectual advances spread among communities of researchers and innovators. A significant body of work has shown that distance matters when it comes to the dissemination of knowledge. Advances are more likely to be noted by those nearby the advance’s origin.

Now a new study co-authored by an MIT assistant professor adds a wrinkle to this issue: National and state boundaries have a distinctly limiting effect on knowledge spillovers, as revealed by an examination of roughly 30 years of data on patent citation. A patent is less likely to be cited by someone working, say, 100 miles away from its point of origin if that distance means crossing a state line, within the United States, or a country line, around the world. The spread of knowledge has a clear geopolitical shape.

Graphic: Christine Daniloff

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