One of the datapoints Lynn uses in his analysis is his own study, of Ethiopia (1994, 250 subjects, ages 15 and 16, IQ 67; no collaborators). He does not appear to considered any systematic effects that may have contributed to such a low IQ, and has used it as a datum in reaching his conclusion about National IQ being a leading cause of per captita GDP differences.
There was a famine in Ethiopia in 1984/5; 10 years before Lynn did his work. His subjects would have been ~5 at the time of the famine. Lynn elsewhere makes it quite clear that such severe environmental factors as famine will certainly impact IQ; hitssquad and others have also quoted results showing that early childhood is a critical time.
Is Lynn being disingenuous in including a datapoint he clearly knows is anomolous? One's suspicion is heightened by reading further in Lynn's discussion; South Korea, Singapore, South Africa are called out for special attention (it's not clear that those datapoints are anomolous), yet Ethiopia is not.
A final comment: Lynn states "Intelligence has increased considerably in many nations during the twentieth century and there is little doubt that these increases have been brought about by environmental improvements, which have themselves occurred largely as a result of increases in per capita incomes that have enabled people to give their children better nutrition, health care, education and the like." Yet he uses data from many pre-1978 IQ studies (20 years before his normalised GDP per capita figures), without correcting for an effect he himself acknowledges! Further, most of the pre-1977 studies are of African children, or otherwise yeilded low IQs!!
What do other PF members think? Is there enough evidence - from Lynn's own writing - to conclude that his conclusions are seriously flawed, not least by many separate inconsistencies, and an apparent failure to address obvious systematic effects?