On the effects of wealth on the B-W gaps, a response to questions posed by a commenter

Max, a commenter, asked:

Could you do an analysis on racial differences in educational outcomes after controlling for parental education, parental occupation, household wealth, neighborhood wealth, neighborhood education, single parent status, native language etc.? I’ve seen you control for family income and parental education (and occasionally both), but I’ve never seen you control for more beyond that (perhaps I’ve missed something!). In Chapter 16 of Affirmative Action for the RichThe Future of Affirmative Action, Dalton Conley of New York University used the Panel Study of Income Dynamics to show that parental wealth (not income) and parental education are the best predictors of college completion, which means that they may also be good predictors of other educational outcomes. He also discussed the data showing that racial wealth gaps are much larger than racial income gaps, which implies that wealth could account for a larger portion of the achievement gap than income. Could you do a similar analysis for IQ? The reason I’m asking for all this is that Carnevale and Strohl control for all of these factors and are left with a very small race effect: http://www.tcf.org/assets/downloads/tcf-CarnevaleStrivers.pdf

I have heard this bit about wealth before.  I am deeply skeptical that wealth can mediate much, if any, of the B-W gap.

Before I dig into this though, let’s take a very brief look at some of the studies Max cited (see here and here) :

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County level homicide rates by race/ethnicity of victim

In my last post, I plotted the overall US county-level homicide rate (all groups combined) by racial/ethnic demographics.  Much of that correlation is being driven by high black-on-black homicide rates throughout the country.

If I plot the rate by the race/ethnicity of the victim this pattern becomes clear and the group-level correlation weaken somewhat (especially asians and whites), but it’s still there…



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A quick post on gun related homicides

While I am personally ambivalent about gun ownership and suspect it plays an incremental role in relative differences between countries/regions/etc (holding other things roughly equal), I thought I’d add some perspective into this argument about the presumed causality of gun ownership on homicide rates.

Mother Jones analysis includes gun suicides and makes no attempt to correct for even course-grain racial/ethnic confounds.

I downloaded the 2009-2013 data for gun-related homicides by race/ethnicity from the CDC’s WONDER database  and compared it to the gun ownership rate data via wikipedia.


I do not feel like doing a lengthy analysis here and now, but suffice it to say that once you remove suicides and race/ethnicity from the equation the case gets much weaker.

There is no evidence of a positive correlation here for blacks and hispanics (if anything somewhat negative).

There is a positive correlation for non-hispanic whites (r=0.45), but it pales in comparison to the racial/ethnic differences here.  To put this into perspective, amongst non-hispanic whites (the bulk of the gun owners in most states), states with the highest gun ownership rates have just 1 death per 100,000 more than states with the lowest rates (on average).

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On sex differences within California public schools

A year or two ago I read an article which demonstrated that sex differences in math and reading achievement are inversely related within and across countries on the PISA tests.  The smaller the male-female math gap, the larger the verbal gap and vice versa.  This tends to support the view that there are innate underlying differences in average abilities and interests between the sexes that strongly influence these patterns.


Google Chrome



Google Chrome

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A (very) brief exploratory analysis of NLSY97 height data

The NLSY97 data provides height information for both biological parents and students at yearly intervals, so I thought I’d take a look at that data.


It looks very much like heritability increases with age here (unsurprisingly).  Around age 13 the slope is relatively flat, especially for boys, but it slowly increases and by age 21 (give or take) there is a rather stark contrast.

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On educational attainment rates and income as a causative factor

As I mentioned to Robert VerBruggen in his latest piece on educational attainment and income, I do not believe that economic concerns are a major cause of differences in education attainment rates by income.

I previously analyzed this and related issues using the ELS:2002 data, but I decided to extend my analysis with NLSY97 and clarify my views, now that I have marshaled a fair amount of data to support my arguments.


Although the IQ (ASVAB) is an excellent predictor and generally mediates these differences fairly well, there are other systematic differences that are not fully accounted for when you control for IQ.   High SES people, whether measured by income or educational attainment, typically have higher GPAs even with the same test scores.



(these differences would likely to be larger still if I did this as a composite SES index using education, income, occupational prestige, etc)

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IQ, test scores, GPA, income, and related correlations from NLSY97

Diving into the NLSY97 dataset a bit right now and I thought I’d share some plots pertaining to IQ/achievement tests, income, GPA, educational attainment, and more.   Nothing here is particularly novel, if you’ve looked for this sort of data before, but sometimes it’s nice to have additional independent analysis or alternative presentations of the data.

High school GPA-test score relationships

HS GPA by ASVAB in percentiles (IQ test)


HS GPA by PIAT (Peabody Individual Achievement Test, IQ test admin. in early childhood)


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