Presuming an average national IQ of 98 led to estimates for mean white IQ by state that appeared to be too high. Instead of norming at 100, the results normed 102.
The US mean score of 98 was taken from the compilations of Lynn and Vanhanen. Their data is a over a generation old now, and the demographic composition of the US has changed in the intervening decades. Assuming a national estimate of 96 yields mean IQ estimates from equally weighted NAEP mathematics and reading scores among public school 8th graders as follows:
That fits quite nicely with the general consensus among intelligence researchers, so 96 is the US mean IQ estimate that will be used in subsequent posts drawn from NAEP data.