Recent research has reported positive effects on schooling due to in utero protection
from iodine deficiency resulting from iodized oil capsule distribution in
Tanzania. We revisit the Tanzanian experience by investigating how these effects
differ over time and across surveys; across different treatment specifications; and
across additional educational outcome measures. Contrary to previous studies, we
find that the estimated effects tend to be small and not robust across specifications
or samples. Using all available data and a medically motivated iodine depletion
function, we find no evidence of a positive long-run effect of iodine deficiency protection
on educational attainment.