Economists build a database from 4000-year-old clay tablets, plug it into a trade model, and use it to locate lost bronze age cities.

They had clay tablets from ancient merchants, saying things like:

(I paid) 6.5 shekels (of tin) from the Town of the Kanishites to Timelkiya. I paid 2 shekels of silver and 2 shekels of tin for the hire of a donkey from Timelkiya to Hurama. From Hurama to Kaneš I paid 4.5 shekels of silver and 4.5 shekels of tin for the hire of a donkey and a packer.

This allowed them to measure the amount of trade between any two cities.

Then they constructed a theoretical model of the expected amount of trade between any two cities, as inversely propotional to the distance between the two cities. Given the data on amount of trade, and the locations of the known cities, they are able to estimate the lost locations:

As long as we have data on trade between known and lost cities, with sufficiently many known compared to lost cities, a structural gravity model is able to estimate the likely geographic coordinates of lost cities [….]

We build a simple Ricardian model of trade. Further imposing that bilateral trade frictions can be summarized by a power function of geographic distance, our model makes predictions on the number oftransactions between city pairs, which is observed in our data. The model can be estimated solely on bilateral trade flows and on the geographic location of at least some cities.

Gojko Barjamovic, Thomas Chaney, Kerem A. Coşar, Ali Hortaçsu, Trade, Merchants, and the Lost Cities of the Bronze Age, 2017

Added to diary 15 January 2018