And educational status is strongly predicted by IQ in the U.S. EDIT: And since IQ is strongly influenced by genetics, this latest data suggests the U.S. is creating a genetic underclass. Taken far enough, this is the death of the republic.
Under IQ 90, 40% drop out of high school. Above IQ 110, less than 1% drop out of high school.
Percent with bachelor's
degree by IQ (ignoring
Source: NLSY project, early 1980s, as analyzed in The Bell Curve in the mid 1990s.
Yes, but as the source explains, the AFQT has several sub-tests, and most of them are highly correlated to IQ. (A few, like the automotive knowledge test, are uncorrelated with IQ.) They claim that appropriate analysis of results on the sub-tests allows a reasonably accurate measurement of IQ to be made.
EDIT: Re-checking the source, they mention that in 1989 the armed forces rescored the AFQT to make it more g-loaded and repeatable. The first draft of the book used the 1980 scoring, but they redid it all using the 1989 scoring because it was superior.
So there is something I wonder about: is there an IQ "floor" below which very few people will be able to benefit from or even complete this sort of education? What percentage of the population falls under this floor? And what will they be doing in the future as both the "service" and manual labor sectors, the traditional absorbers of people with no degrees or impractical "soft" degrees, dwindle in the number of people employed?
And who is doing the political squeezing? A cognitive elite that are being efficiently skimmed off and segregated by IQ in late childhood. This bodes poorly for the stability of the nation.
You're leaping across logical gaps here. IQ can be predicted by a number of factors (parental wealth, IQ, and education are a few), and research on intelligence is fraught with identification problems. It's hard to believe claims of a "genetic underclass."
There have been several large studies of identical twins separated at birth. For a given twin, the strongest correlate of IQ is the other twin's IQ. Likewise, the non-identical but biologically-related siblings do have moderately correlated IQs. However, there is barely any correlation between a twin and their adoptive parents or siblings. This suggests that genetics and prenatal environment determine most of IQ.
There is also strong evidence from gene sequencing that genetics directly affects IQ. Genes that affect sphingolipids, chemicals important in the brain, are known to affect IQ. A variation in the SNAP-25 gene has been found to increase intelligence by an average of 3 IQ points.
And while it has become a cliche, it is still true that correlation is not causation: coming up with correlation is easy, but solid scientific works need to prove that the correlation is not spurious. Most studies don't (this is sadly not specific to discussions about IQ, and is a plague of many studies in too many areas - good statistics are hard).
Yes, and I am closely acquainted, through attending their graduate student "journal club,"
with most of the researchers who have conducted the best of those studies. An earlier reply of mine here on HN
corrects (with citations to current research publications) some of the overstatements seen in popular literature about what twin studies show. There is also not any single gene variant that has large effect on IQ, in the view of those researchers about what the most up-to-date gene association studies show.