(Washington Post) Prosperity begets prosperity: On a global level, economists and historians have shown that places that prospered 100, 500, even 1,000 years ago tend to be more economically developed today.

But how? We’re less clear on the exact channels by which economic activity sustains itself over the millennia. Could dynastic wealth play a role? How about the concentration and transmission of knowledge via institutions such as schools and libraries? How does military might factor in?

Now, a team of Danish economists has put forth a forceful case for one largely overlooked driver of economic development in Europe: roadways built by the Roman empire nearly two thousand years ago. They demonstrate that the density of ancient Roman roads at a given point in Europe strongly correlates with present-day prosperity, as measured by modern-day road density, population density and even satellite imagery of nighttime lighting.

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