A very interesting paper. My first reaction is that the effect of salt iodization is just too large—that iodine deficiency in utero is highly unlikely to rob you of 11% of your lifetime income. Thus I suspect that something has gone wrong with the identification. But I cannot figure out what. Great kudos to Nguyen and company for being willing to put this out there for us to look at: Achyuta Adhvaryu, Steven Bednar, Anant Nyshadham, Teresa Molina, Quynh Nguyen: When It Rains It Pours: The Long-run Economic Impacts of Salt Iodization in the United States: "In 1924, The Morton Salt Company began nationwide distribution of iodine-fortified salt...

...Access to iodine, a key determinant of cognitive ability, rose sharply. We compare outcomes for cohorts exposed in utero with those of slightly older, unexposed cohorts, across states with high versus low baseline iodine deficiency. Income increased by 11%; labor force participation rose 0.68 percentage points; and full-time work went up 0.9 percentage points due to increased iodine availability. These impacts were largely driven by changes in the economic outcomes of young women. In later adulthood, both men and women had higher family incomes due to iodization...."