A large literature characterizes urbanisation as resulting from productivity growth attracting rural workers to cities; these authors think it is in reverse: when rural workers move to cities, the resulting urbanisation yields productivity growth

Urbanisation and the Onset of Modern Economic Growth. Liam Brunt, Cecilia García-Peñalosa. The Economic Journal, ueab050, June 30 2021. https://doi.org/10.1093/ej/ueab050

Abstract: A large literature characterizes urbanisation as resulting from productivity growth attracting rural workers to cities. Incorporating economic geography elements into a growth model, we suggest that causation runs the other way: when rural workers move to cities, the resulting urbanisation produces technological change and productivity growth. Urban density leads to knowledge exchange and innovation, thus creating a positive feedback loop between city size and productivity that initiates sustained economic growth. This model is consistent with the fact that urbanisation rates in Western Europe, most notably England, reached unprecedented levels by the mid-18th century, the eve of the Industrial Revolution.