To what extent do tropical diseases contribute to the poverty characteristic of tropical countries? Estimates of the impact of health on income are difficult to obtain because health is a normal good-countries with higher income will buy more of it-and third factors such as remoteness and bad government might impede both productivity and public health. In the Abuja Declaration of 2005, African heads of states claim that malaria has depressed income growth in Subsaharan Africa since the 1960s, so much so that GDP in the region today is 40% lower because of malaria. Estimates of this magnitude have been mocked at cocktail parties and clambakes. But how ridiculous is this number?

This study considers the eradication of hookworm disease from the American South as a test of the quantity-quality (Q-Q) framework of fertility. Eradication was principally a shock to the price of quality because of three factors: hookworm (i) depresses the return to human-capital investment, (ii) had a very low case-fatality rate, and (iii) had negligible prevalence among adults. Consistent with the Q-Q model, we find a significant decline in fertility associated with eradication. Relative sizes of fertility and human-capital responses to hookworm indicate that the Q-Q mechanism is of a similar magnitude to secular co-movements in these same variables.