What's important to note here is that, assuming normal distribution, group differences can account for large differences in the number of individuals at the ver

What's important to note here is that, assuming normal distribution, group differences can account for large differences in the number of individuals at the very top (and bottom). If a group A has a mean IQ of 100 and group B has a mean IQ of 110, group B will have four times more individuals with IQ over 130 than group A.