others include possibly long-term effects due to protracted separations from the labor force and disengagement from economic activities.

Two studies by Bleakley (in Spence and Lewis, forthcoming) examine the effects of diseaseeradication campaigns on health and economic outcomes; his results suggest that improving health could be important for growth on the margin but is unlikely to be a panacea. In his 2007 study of the impact of hookworm eradication efforts under the Rockefeller Sanitary Commission in the American South in the early twentieth century, Bleakley measures the infection rates that prevailed before the intervention; on average, 40 percent of school-age children were infected. Like Acemoglu and Johnson (in Spence and Lewis, forthcoming), he uses data on infection rates by location, which reflect the geographic variation in potential benefits from hookworm eradication, to identify the impact of changes in the health environment on economic outcomes.

Bleakley finds that areas with higher preexisting infection rates saw greater increases in school enrollment, attendance, and literacy after the intervention. For example, he finds that school attendance before 1910 was negatively correlated with 1913 infection rates, but that by 1920 the 1913 infection rates did not predict attendance. That is, those areas that had more to gain from hookworm eradication saw their school enrollment rates increase more. Bleakley finds similar results for literacy. Other changes in the economic environment could have led to similar trends over this period, but he argues that, if so, these influences would have affected adults in different areas in similar ways. However, he finds no similar pattern among adults across the affected areas who, by the nature of the disease, had virtually no preexisting infection.

Bleakley (2006b) undertakes a similar exercise focusing on the malaria eradication campaigns in the United States circa 1920 and in Brazil, Colombia, and Mexico circa 1955. Preexisting prevalence rates across regions, combined with a paced eradication campaign across the U.S. South, which provide exogenous variation, permit him to identify the impact of childhood exposure to malaria on future adult literacy and incomes. He finds that, among individuals born well before the relevant eradication campaign, those born in more malarial regions had lower wages and lower literacy rates later in life, while among individuals born well after the campaigns, malaria prevalence before the eradication campaign had little effect on future wages and literacy. He concludes, “Persistent childhood malaria infection reduces adult income by 40 to 60 percent.” Bleakley is able to differentiate the impact of morbidity from that of mortality on future income. He finds that eradication of _vivax_ malaria (which causes high morbidity, but relatively few deaths) leads to significant increases in human capital formation and future income, but that eradication of _falciparum_ malaria (which is often fatal) produces no such gains. To explain this result, he argues that, although reductions in mortality rates increase the marginal benefit of human capital acquisition (because people who survive have more years in which to earn a return on human capital investments), this might have little impact on the level of investment if marginal costs are rising steeply. By contrast, a reduction in morbidity makes it easier to attend school and to learn while there, thereby flattening the marginal cost curve and leading to significant increases in human capital acquisition.

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