@thomas_chaney and I updated our working paper on "Trade and the...
Johannes Boehm@johannesmboehm
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May 11, 2026
~2 min read
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@thomas_chaney and I updated our working paper on "Trade and the End of Antiquity" (which recently got some airtime here). A short re-cap: 1/n
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We use archaeological data on the flows of coins to study what happened around the Mediterranean between the 4th and 10th century, a time when economic activity shifted away from the Mediterranean (the "End of Antiquity").
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We find that coin flows exhibit very similar properties as modern-day trade flows (gravity); not too surpising given that coins were the main medium of exchange for long-distance trade.
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The patterns of coin flows change sharply around the time of the Arab conquests (yep, border effects!) in line with a trade disruption. Pirenne's famous thesis (Arab conquests => End of Antiquity) comes to mind! But could trade have been really that important?
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As trade economists know, "trade data" is useful beyond studying trade flows: you can back out eg. relative productivity.
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We build on work by the late Jonathan Eaton (& Kortum & Dekle) and propose a model where real per capita consumption can be decomposed into technology, trade openness, and trade deficit. Under some assumptions we can identify each term from the coin data.
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Estimating the model, we find large declines in real consumption in the Roman-Byzantine heartlands in the eastern Mediterranean, and increases in the Frankish lands. We see the "End of Antiquity" in our estimates!
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The decomposition tells us that Byzantium's decline is due to a decline in openness, but even more so declines in productivity and seigniorage. For most other regions, including the ascent of Francia, it's mostly productivity changes that are driving things.
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Finally, we compare our estimated changes with data on relative urbanization based on city sizes (like much else, these measures are very rough... all this is >1000y ago). We were surprised that they lined up quite closely!
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Full draft is here: jmboehm.github.io/coins.pdf n/n
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tagging @jp_koning @florianederer @pseudoerasmus cause you tweeted about it (thanks!)