The Effect of Mandatory Iodine Fortification on Cognitive Test Scores in Rural India

This paper is the first to provide evidence of a direct causal impact of iodine fortification in early life on cognitive skills in childhood. I apply a differences-indifferences strategy using exogenous variation from a nationwide iodine fortification policy in India, comparing test scores of school aged children in naturally iodine sufficient and deficient districts over time. I find that the policy increased the probability of attaining basic numeracy and literacy skills by 2.67 - 5.83%. Previous papers find a larger effect on longer term human capital for women. I do not find a gender differential for basic skills but I observe a positive effect on more difficult literacy tasks for girls but not for boys. Additionally, I find that the male treatment effect on basic numeracy vary with district level son preference.