In terms of educational outcomes, 2nd generation Blacks are on parity with native whites. Since education is a good predictor of IQ, this is prima facie evidence for intellectual equality. This in turn has implications of various racial hereditarian hypotheses.
1. Immigrants, from different regions, vary in terms of their selectivity for a given trait. Let’s call this s. There are a number of ways to measure s with varying degrees of reliability. If we wanted to know the educational s for immigrants from different regions, we might compare the probability that an immigrant will be skilled — i.e. have a BA or higher — to probability that a resident of his native country will be skilled and then convert this into a standardized metric.
s gives us a standardized estimate of how much an immigrant population deviates, in some trait, from the population from which it hailed.
2. Since offspring regress towards the mean, for a given trait, the offspring of immigrants will congenitally deviate from their parent’s native population by s times the narrow heritability of the trait in that population. Let’s call this deviation d1. (So if the educational attainment s for East Asian (EA) immigrants is 1.6 and the narrow heritability of attainment is .5 in both native and diasporic EA populations, 2nd Gen EAs abroad should be, genetically, .8 SD superior to native EAs, in this trait.)
3. 2nd Gen populations will phenotypically deviate from the resident population by some magnitude. Let’s call this deviation d2. (So according to the 2009 census, 2nd generation Asians between ages 24 and 35 obtained .5 SD more college degrees than 3rd+ generation Whites in the US.)
4. Assuming similar narrow heritabilities across populations — obviously a more problematic assumption for traits like educational attainment than g — the genetic deviation between two native populations can be roughly estimated as the difference between d2 and d1. (In the case of native East Asians versus native Whites, the difference would be 0.5 – 0.8 or -.3 SD in genetic potential for attainment.) (Just going with the data here folks.)
5. So if 2nd generation Blacks are on parity with native US whites with respect to IQ, Black Africans and White Americans differ by (0 – d1) or (d1) or (.6 x s).
6. The s for IQ can be estimated by comparing National IQs to immigrant IQs — if data on the latter can be found. The assumption being that IQ tests are no more biased against residents of a country than emigrants from that country.
7. If in the West Indies and in Africa, the average measured Black IQ ranges from 70-80, and the average measured Black Immigrant IQ ranges from 85-95, the s for IQ would be 1. Or immigrant Blacks would represent the upper 1/3rd of their population in terms of phenotypic IQ. (2.2 SD being the distance between the upper and lower 3rds of a normal distribution.)
8. Assuming a global narrow heritability of g of .6, from point (5) and (7) we get a racial difference of 0.6 SD or 10 points — significantly less than what is often argued.