Sunday, April 26, 2009

Race and IQ trends

Whites, N =19,726

Blacks, N = 3,441

As a follow-up to the last post, let's look at IQ trends by race since the GSS vocabulary test was first given in 1974 (WORDSUM). The test is 10 questions. The overall mean for whites is 6.3. Over the 35-year span, the percentage of whites with below-average scores has dropped about 5 points, and the top two categories have shrunk about the same. The average-to-above-average has picked up the slack.

For blacks (bottom graph), the overall mean is 4.9. The share scoring 4 or fewer has dropped over the period from around 45% to 30%. The improvement began in the late 80s. The percent scoring 5 or 6 grew from 38% to 58%. That's the good news. The bad news is that those scoring 7 or higher appears to have shrunk. (It's not easy to tell since few blacks score so high, so there is a lot of year-to-year fluctuation).

So, the main story seems to be that both blacks and whites have expanded their middles at the expense of their extremes. Next, let's look at mean changes by year:

Mean IQ (standard deviation in parentheses)
1970s 6.2 (2.2)
1980s 6.1 (2.2)
1990s 6.3 (2.0)
2000s 6.4 (2.0)

1970s 4.6 (1.9)
1980s 4.7 (2.1)
1990s 5.0 (1.9)
2000s 5.2 (1.9)

The past three or four decades have been good for blacks. Their mean has increased more than whites, and so the IQ gap has narrowed from 1.6 in the 70s to 1.2 in this decade. Another way to look at it is the gap in standard deviation units (SD). The gap fell from .72 SD in the 70s to .60 SD now. The narrowing is significant, but the gap is still large.

It's also important that, while the white mean has gone up a bit since the 70s, the standard deviation is now smaller. This is due to fewer whites having low scores, but it is also due to a smaller share of smart people.

It looks like America's efforts may have raised the scores of the bottom half, while ignoring the high end. As La Griffe has shown, a nation's wealth depends on the fraction of the population that is intelligent. So it makes little sense to obsess about the bottom, but that seems to be what we're doing. (I'm not sure what has brought up low scores. Getting rid of really bad schools still around in the 60s? Nutrition? All that TV watching improving vocabulary?).


Lover of Wisdom said...

Is it possible to check how the narrowing for the black-white gap in WORDSUM scores measures against the narrowing for the black-white gap in SAT, GRE, and traditional IQ scores?

I'm interesting to see if the narrowing is similar.

The Undiscovered Jew said...

It looks like America's efforts may have raised the scores of the bottom half, while ignoring the high end.I wonder if abortion has been culling lower IQ blacks since Roe vs Wade?

As for white women,

High IQ white women have shorter de facto fertility lifespans because they spend so much time in college, especially white women over 130 IQ. (Richard Lynn has claimed there is a dysgenic trend among the most intelligent East Asians, so this phenomena is not limited to the West.)

The reason women lose their fertility in their mid 30's is because egg quality starts to decline rapidly from a woman's late 20's onward. (It should be noted that the Uterus does not decline in childbearing quality until the late 40's. The problem of infertility is mostly due to declining egg quality)

The solution is to extend white women's fertility from the late 30's to the late 40's by using new Artificial Reproductive Technologies.

Such techniques would include freezing eggs and or ovarian tissue when women are young, creating affordable ways to extract large numbers of eggs from young white egg donors for older women, and using adult stem cells to restore women's fertility.

Pin said...

Thats interesting. If anything, the literature out there explains that the gap has gotten even wider in recent years because of lack of control at the bottom(70 IQ women).

SAT scores show the same wide and not narrowing gap since the 90s.

P. Rushton in the G factor put it at 1.2SDs based on Ravens Matrices taken in the 80s so halving it is unlikely.

However this shouldn't hold back NAMs or Arabs. There was an interesting article in the New Yorker about "neuroenhancers" aside from Ritalin to be out by 2012. This is probably the best bet.

Anonymous said...

"As La Griffe has shown, a nation's wealth depends on the fraction of the population that is intelligent."

I wouldn't say he's shown it: he's argued for it, but a thesis that sweeping can't be established on the basis of a couple of essays.

Ron Guhname said...

He's done sophisticated data analyses, not essays. That's a tad more persuasive than empty skepticism.