Iodized salt has large impacts on child health and test scores in Ethiopia
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This study quantifies the impact of iodized salt on child survival and academic achievement based on sudden nationwide changes in access to iodized salt, given naturally occurring geographic variation in iodine. We combine data on birth timing and test scores on national school-leaving exams from 2003 to 2019 with child health surveys and newly collected measures of soil and grain iodine concentrations, finding that children with longer exposure to iodized salt in utero and infancy during the 1990s went on to have lower mortality and higher scores, especially in places with less iodine in locally grown food. Among children with the longest exposure, our main estimates show a national average test score gain of 0.09 standard deviations from widespread iodization, with an additional gain of 0.08 standard deviations for each standard deviation reduction in soil iodine. Placebo tests confirm that effects are specific to iodine (vs. selenium) and specific to cognition and survival (vs. height and weight, which are not affected by iodine deficiency). This provides the first large-scale evidence of how educational achievement is affected by national salt iodization programs recommended by the World Health Organization but not yet universally implemented.
