ARTICLE: "In Raising the World's I.Q., the Secret's in the Salt," by Donald G. McNeil, Jr., New York Times, 16 December 2006, p. A1.

A third of the globe, roughly 2 billion, don't get enough iodine (available in iodized salt), so 10-15 I.Q. points are shaved off, on average. Having enough during pregnancy is the best way to avoid mental retardation. Hundreds of millions in India and China alone suffer this fate, but other than India, all of the other "severe to moderate deficiency" states are located--no surprise--in the Gap. But things can be fixed. Russia's parliament recently decides to make iodized salt mandatory. China's ten-year effort raises the percentage of people using iodized salt to over 90 percent. Africa's fate is typical: no shortage of iodized salt because Kenya and South Africa export it, and yet half of the nations are mild to severe in the deficiency. Update: Steve also posted on this article recently: Iodine and Intelligence