The Impacts of Hookworm Eradication in the American South. A replication study of Bleakley (The Quarterly Journal of Economics, 2007).
by David Roodman
Through designs akin to difference-in-differences, Bleakley (2007) produces evidence that the campaign to eradicate hookworm from the American South circa 1910 boosted school enrollment in childhood and income in adulthood. This comment works to replicate and reanalyze that study. Innovations include incorporation of the larger U.S. Census samples now available, and fitting of specifications focusing more sharply on the timing of any effects of the campaign, which are the basis of the most credible identification. The long-term convergence between historically low- and high-hookworm areas documented in Bleakley (2007) began decades before the campaign and did not accelerate in a way that would invite hookworm eradication as an explanation. Likewise, in the case of adult income, the convergence continued for decades after. In sum, hookworm eradication did not leave a telltale imprint on the historical record assembled here.