The Growth Tide: Quasi-Experimental Evidence on the Regional Economic Impacts of Mega-Dams

Large-scale hydropower dams are among the most costly and controversial infrastructure projects, yet credible evidence on their regional economic impacts is scarce. This paper provides the first quasi-experimental estimate of the impact of the Three Gorges Project—the world’s largest dam—on regional economic growth. Using a difference-in-differences design with county level data, we find that the project raised GDP per capita in directly affected counties (which account for 11.6% of China’s GDP) by 9.1%. These gains were driven by improved navigation and trade, industrial land creation, and a moderated local climate—not merely by increased electricity supply. The project has also significantly accelerated the economic shift from agriculture to industry and services. However, the benefits were starkly unequal: downstream counties saw a 13.8% increase, while upstream counties experienced negligible gains, a divergence explained by asymmetric changes in land avail able for development. A cost-benefit analysis shows that considering only direct power revenues yields a negative return (-65.5%), but incorporating regional growth spillovers reveals a strongly positive return of 322.3%. Our findings demonstrate that the economic justification for mega-dams hinges on their indirect growth effects, which are large but spatially concentrated.