One of every two preschool-aged child and pregnant woman is iron-deficient
"Therefore, the WHO estimates that one out of every two preschool children and pregnant women in developing countries are iron deficient. The highest prevalence of anemia is in preschool-age children (47%); however, the population group with the greatest number of anemic individuals is non-pregnant women (468 million)"
"Iron," HarvestPlus, last modified 2015, accessed June 11, 2015, http://www.harvestplus.org/content/iron.
Also see http://www.harvestplus.org/content/nutrients for a heat map of combined nutrient deficiency in iron, vitamin A, and zinc.