The Cognitive Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States
AbstractIodine deficiency is the leading cause of preventable mental retardation in the world today. The condition, which was common in the developed world until the introduction of iodized salt in the 1920s, is connected to low iodine levels in the soil and water. We examine the impact of salt iodization on cognitive outcomes in the US by taking advantage of this natural geographic variation. Salt was iodized over a very short period of time beginning in 1924. We use military data collected during WWI and WWII to compare outcomes of cohorts born before and after iodization, in localities that were naturally poor and rich in iodine. We find that for the one quarter of the population most deficient in iodine this intervention raised IQ by approximately one standard deviation. Our results can explain roughly one decade's worth of the upwardtrend in IQ in the US (the Flynn Effect). We also document a large increase in thyroid related deaths following the countrywide adoption of iodized salt, which affected mostly older individuals in localities with high prevalence of iodine deficiency.
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Date of creation: Jul 2013
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This paper has been announced in the following NEP Reports:
- NEP-AGR-2013-07-20 (Agricultural Economics)
- NEP-ALL-2013-07-20 (All new papers)
- NEP-HIS-2013-07-20 (Business, Economic & Financial History)
- NEP-NEU-2013-07-20 (Neuroeconomics)
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- Hoyt Bleakley, 2007. "Disease and Development: Evidence from Hookworm Eradication in the American South," The Quarterly Journal of Economics, MIT Press, vol. 122(1), pages 73-117, 02.
- Bishai, David & Nalubola, Ritu, 2002. "The History of Food Fortification in the United States: Its Relevance for Current Fortification Efforts in Developing Countries," Economic Development and Cultural Change, University of Chicago Press, vol. 51(1), pages 37-53, October.
- Erica Field & Omar Robles & Maximo Torero, 2009. "Iodine Deficiency and Schooling Attainment in Tanzania," American Economic Journal: Applied Economics, American Economic Association, vol. 1(4), pages 140-69, October.
- Dimitra Politi, 2011.
"The Impact of Iodine Deficiency Eradication on Schooling: Evidence from the Introduction of Iodized Salt in Switzerland,"
ESE Discussion Papers
200, Edinburgh School of Economics, University of Edinburgh.
- Politi, Dimitra, 2010. "The Impact of Iodine Deficiency Eradication on Schooling: Evidence from the Introduction of Iodized Salt in Switzerland," SIRE Discussion Papers 2010-02, Scottish Institute for Research in Economics (SIRE).
- Watson, Tara, 2006. "Public health investments and the infant mortality gap: Evidence from federal sanitation interventions on U.S. Indian reservations," Journal of Public Economics, Elsevier, vol. 90(8-9), pages 1537-1560, September.
- Morgan Kelly & Joel Mokyr & Cormac Ó Gráda, 2013. "Precocious Albion: a New Interpretation of the British Industrial Revolution," Working Papers 201311, School Of Economics, University College Dublin.
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