The USA, the UK, and Denmark are not the only countries to see an observable decline in average IQ:
- Dutton and Lynn have identified a 4 point decline in French IQ.
- Dysgenics and replacement migration are proposed as causes.
- French IQ losses are found to be associated with the Jensen effect (ρ = .833).
- A common factor of g loadings and 3 biological variables loads on the loss-vector.
- This supports biological causation.
Dutton and Lynn report secular declines in Fullscale IQ evaluated using WAIS of four points a decade in France between the years 1999 and 2008–9. It is posited that the trend may have a partially biological cause, stemming from dysgenic fertility and, to a lesser extent, replacement migration. Given that these, and other biological phenomena are associated with the Jensen effect, it is expected that if they are the principal causes of the IQ decline then the secular change should also be associated with the Jensen effect.
Furthermore if it can be demonstrated that the vectors of secular IQ decline, g loadings and the vectors of other biological indicators share variance, then the case for biological causation will be strengthened. Using the method of correlated vectors and error disattenuation, the secular IQ declines are shown to be associated with a high-magnitude Jensen effect (ρ = .833). A multi-vector common factor comprised of the vector of g loadings along with the vectors of three biological variables (subtest heritabilities, dysgenic fertilities and simple visual reaction times) was found to load substantially on the secular IQ decline vector (λ = .723).
These findings indicate that the French secular IQ loss likely has a primarily biological cause.
What is frightening about this decline in French IQ is how rapidly it has taken place. My estimate of a post-1965 four-point IQ loss in the USA was a minimum estimate based solely on replacement migration, but considering that dysgenic fertility is also a factor in the USA, the actual decline is almost certainly worse.
If replacement migration is also the lesser factor in the US case, then the post-1965 IQ decline in the USA could be as much as 10 points. However, US immigration has been higher and US native birth rates have remained higher than in France, so something on the order of 7-8 points is more likely. This is not insignificant; it is the difference between the current USA and Sierra Leone.
Immigration isn’t just bad for a nation’s economy, it is horrifically damaging to a nation’s prospects for the future.