Relying on Richard Lynn’s work Dysgenics: Genetic Deterioration in Modern Populations,
the relaxation of internal selection is thought to have begun around 1850 as the fertility of the lower classes exceeded the upper classes because of improvements in hygiene and reduction in diseases. He cites Lynn’s estimate that England lost 6.9 IQ points over 90 years (1920-2010) and estimates that Denmark’s average IQ dropped around 10 points since 1850 due to internal relaxation of natural selection.
However, the main point of the paper is to evaluate the influence of non-Western immigrant population on IQ. Nyborg estimates that by 2072 around 60% of births in Denmark will be to people of non-Western origin, and Danes will be a minority by 2085. This is due to markedly higher birth rates among non-Western immigrants and their descendants – nearly 4 times greater than the native Danes. Moreover, Nyborg projects that the low IQ (70–85) immigrant share of the population will grow steadily to nearly 60% of the share of all births by 2072.
This implies a drop in IQ for the entire population. Especially chilling is his Figure 5 which shows a dramatically increasing number of Danish citizens in the 70-85 IQ range. This IQ band is projected to be the majority of the population not long after 2075 and to dominate the school system by 2050.
The grim conclusion is that in the period from 1850 to 2072 there will be a total phenotypic decline of 15.39 IQ points. Given a heritability of 0.82 for IQ, this means genotypic damage of 12.62 IQ (i.e., 15.39 X .82) points from the internal relaxation of natural selection. Foreign immigration adds another 6 IQ points, including nearly 5 IQ points in genetic decline . The projection then is for an average population decline of around 21 IQ points and around 17 points in genetic potential for IQ since 1850.