AI buildout exceeds railroad-era share of GDP, yet economic impact lags far behind

emollick · x · 2026-09-29

Ethan Mollick notes that the current AI buildout, as a share of GDP, is larger than railroads at their peak — yet AI's dominance of the economy is nowhere near rail's. In 1890, 1 in 12 American men worked in railways, which consumed 56% of all machine horsepower in the country. The comparison raises questions about whether massive AI capex can deliver returns matching its historical scale.

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