IQ of 100 is defined as the mean IQ, and as such it is always moving. The trend is that the mean IQ is rising. But that trend has been delayed in some countries

IQ of 100 is defined as the mean IQ, and as such it is always moving. The trend is that the mean IQ is rising. But that trend has been delayed in some countries. All the factors I mentioned have an impact in IQ. Two more concrete examples: - Nutrition-wise, it is not only about hunger. The addition of iodine in food such as tablet salt, has improved Western IQ by about 15 points. In contrast, iodine deficiency is a problem present in Africa. - Leaded fuel for example had a negative impact on the brain and has been found to affect IQ negatively. Only recently Africa has been transitioning out of leaded fuel. Now, if you are going to be taking a random sample that is representative of a population, everyone within that population has the same probability of being sampled, so the "random kids" you mentioned could perfectly be sampled, and if they're significant in their population that might be reflected in the sample as well.