Disappointment about the war on worms in the American South 100 years ago

On GiveWell.org, I just blogged a new study revisiting the evidence on whether the campaign in the 1910s to rid the South of hookworm brought major benefits. A great 2007 paper by Hoyt Bleakley suggests that it did: after eradication school attendance rose disproportionately in historically hookworm-heavy areas; and adult earnings of babies born in affected areas also later rose.

The new study revisits Bleakley’s original by reconstructing its database from primary sources, and replicating and revising the analysis. I ended up strongly questioning the original study’s conclusion. These two pairs of graphs show why. The first graph in each pair is from the¬† original study, the second from the new version. The original graphs seem to show jumps in outcomes of interest—school attendance, earnings—but the new ones do not.


I have also reanalyzed Bleakley’s study of the impacts of malaria eradication in the U.S., Brazil, Colombia, and Mexico. In that case my results match the original much more. Write-ups coming soon.