Friday, March 14, 2008

IQ and incarceration

One of the recurring topics here is the relationship between IQ and, well, virtually everything that is desirable--a higher material standard of living, greater livability (as measured by a set of 44 variables like average educational attainment and libraries per capita), longer life expectancy, greater physical health, relative income equality and more total wealth, lower rates of illegitimacy, higher rates of employment, and lower rates of infant mortality, just to list those I've looked at.

It's become a bit of a game to search for some positive attribute that correlates inversely with IQ. So far, that search hasn't yielded much. The only arguable exception, total fertility, is a worrisome one, as national birth trends suggest the meek (minded) may indeed inherit the earth. A nation's TFR and estimated average IQ inversely correlate at a vigorous .81.

In any case, the perception of fertility's goodness forms an inverted U-shaped curve, with both low levels (say, a TFR of less than 1.5) and high levels (a TFR of more than 3) causing an increasing level of concern as they move further toward either extreme. The optimal level falls somewhere in between, around the estimated replenishment rate of 2.1. By contrast, trends for all of the conditions listed in the opening paragraph are infinitely more desirable as they continue (until a bane like infant mortality is reduced to zero, of course).

So why not add another notch to the raising-IQ-is-good belt? Pew recently released a report on the US' prison population, with detailed data presented at the state level. Predictably, the report's commentary insinuates that because a large prison population is not a good thing to have, and sticking someone in the slammer for twice as long doesn't seem to have much effect on whether or not he'll commit another crime once he's released, shortening sentences and releasing more inmates is probably the way to go. It'll reduce government spending, too, and that's historically been a primary concern of the Pew Research Center, no?

Apparently neither party in California seems to agree. Seems to me that incorrigible recidivism rates suggest we should move towards, not away from, locking people up and throwing away the keys. But to try and look at the effects of incarcerating criminals without taking demographics into consideration is fallacious. Whatever the optimal percentage of Mississippi's population that 'should' be behind bars given present conditions is, it's not the same percentage that applies to Minnesota.

Media sources are favorably inclined toward Pew for its more-than-acceptable press releases, which gives the center its prestige and continued notoriety. What make Pew so valuable, though, are the hard data it collects. For a research institution to be left-leaning but honest is about as good as it gets!

Much in the report comes as little surprise. Among men 18 and older, blacks are seven times as likely to be incarcerated as whites are. For Hispanics, the multiple to whites is three.

The best predictor of a state's incarceration rate may come as more of surprise, though (if I hadn't already given it away). Economic inequality trends in the expected direction but the relationship isn't statistically significant. Population density has no appreciable effect, either, and actually trends in the opposite direction of what would be expected (greater density means a smaller prison population). It's not the poverty rate (r-value of .59), the illegitimacy rate (.54), the unemployment rate (.29), or the average age of the population (.40), either. It's not even (quite) the percentage of a state's population that is black or Hispanic (.648).

The strongest correlation with incarceration rates that I've been able to find comes from estimated average IQ (.649). Not surprisingly, a state's 'livability' also inversely correlates strongly (.63) with the prisoner population.

Poverty rates are arrived at by use of a rolling average from '04-'06. The rest of the data are from '06, except the incarceration rates from Pew which are from mid-'05, the livability index which is also from '05, and the gini coefficient numbers, which are almost a decade old (but the most recent I could find). Given that McDaniel's IQ estimates* are the least precise of all the data, the actual relationship between IQ and incarceration rates is likely to be stronger still.

The War on Unintelligence, or more palatably, the Crusade for Intelligence, has not yet been forthcoming (or has been comparable to the first wave led by Peter the Hermit in the form of No Child Left Behind). Strategies for raising IQ through the course of a person's life have been met with limited success, and the benefits realized tend to be temporary. I continue to wonder if the reduction in the common use of lead in paint, gasoline, candles, solder, and the like offers an explanation for the Flynn effect and its seeming abatement in the developed world today.

But there are areas in which the incarceration-IQ relationship provides more concrete direction. Regressive tax credits for those with dependents should be made progressive. Why offer an incentive to have children to those least able to afford having them, while removing that same incentive for those who are most able to raise them?

Allowing unskilled immigration from Latin America is destructive. If Hispanics are more than 2.5x as likely to end up in jail as whites are, why should we be taking them in en masse? We should have an immigration policy based on merit, and IQ should factor significantly into determining an applicant's merit level. Make the completion of a Wonderlic test, administered in the country of origin, part of the application process. It's quick, inexpensive, and tests for English language proficiency as well.

Given the report's veiled recommendation that states should temper prison sentences, consider releasing those who are not deemed particularly dangerous, and divert to education the money saved this way, the words of Randall Parker are pertinent:

Anything that could raise average IQ a few points would do more to boost economic growth and lower social pathologies than increased educational spending or the other typical liberal or free market libertarian nostrums.
* For state IQ estimates, I jump back and forth between using Professor McDaniel's estimates and my own. Our estimates correlate almost perfectly at .96, with the slight variance probably representing the superiority of his numbers. But because he arrives at his estimates by using a normal distribution centered on a 100 point scale and derived from NAEP scores directly, his methodology doesn't really work for coming up with estimates for groups that score significantly below the national average (ie, blacks). He has no estimate for DC, for example. So if I'm interested in black or Hispanic estimates, or want to include DC with the other 50 states, I use my numbers. If those sets are not needed, I default to using his.


John S. Bolton said...

Would the correlation be higher if you adjusted for the large numbers permanently deported from prisons, say by using % foreign born in a state? The idea being that those deported out of prisons would otherwise got caught in three strikes laws to such extent that most would otherwise still be in prison now.

mensarefugee said...

Anything that could raise average IQ a few points would do more to boost economic growth and lower social pathologies than increased educational spending or the other typical liberal or free market libertarian nostrums.

Ive long stopped really arguing with Randall, but a free market nostrum like, oh - let people keep the money they make and only give it away out of free will via charity would drop the low IQ illegitimacy rate like a rock. But maybe he was talking in generalities there.

Sleep said...

At the individual level, IQ correlates with several negative health-related variables: myopia, ectomorphy, susceptibility to asthma and allergies, and various other diseases which are especially widespread in the Jewish population.

Audacious Epigone said...


Maybe, if I could get those numbers at the state level. Estimating simply by % foreign-born seems hazardous to me though, since legal residents who are not deported are counted (I believe).


Well, that would have the effect of raising IQ, which I think is what Randall was getting at. The comparison he's going after is between privatizing education versus stopping illegal immigration--which will raise NAEP scores more?


Yes, even left-handedness. Good point. So I suppose you might argue that sufferance from allergens is higher in more intelligent populations (although the latitudinal/IQ relationship might not make that the case!).

Anonymous said...

Steve Sailer posted on lead and IQ a few months ago:

Interesting stuff.

Audacious Epigone said...


Yes, thanks for bringing that post back to mind. That's part of what spurred me into wondering about a potential link between lead and the Flynn effect. While any 'single bullet' theory probably comes up short, there's lots to at least make it plausible that the two are related.

Anonymous said...

Did you mean 'solder' not 'sulder?'

Audacious Epigone said...


Oops. Yes, and thanks. I fixed it.

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