Iodized salt became common in American kitchens, and cases of goiter nearly disappeared. Today, only about 53 percent of table salt sold through retail is iodized.
After trials showed that supplements of iodine could prevent goitre, iodised salt was rolled out commercially in 1924, starting in grocery stores in Michigan.
Most live in environments with low natural iodine levels (such as in parts of sub-Saharan Africa and South-East Asia), or in countries without universal access to iodised salt.