For one, only about half of American table salt (which makes up 11% of the salt Americans consume today) is actually iodised.
首先,只有大约一半的美国食盐(占当今美国人消费的盐的 11%)是真正加碘的。
经济学人 Science and technology
After trials showed that supplements of iodine could prevent goitre, iodised salt was rolled out commercially in 1924, starting in grocery stores in Michigan.