[Updated: I redid this analysis and I updated the file below. Here were the correlations:
While the small sample sizes preclude a definitive conclusion, the results seem to be in accordance with neither the hypotheses of strong colorism nor strong plieotrophy, both of which predict equal correlations between and within families. The results, rather, seem to be more consistent with either shared family effects and/or genetic effects (the later either due to ancestral genetic differences or to cross assortative mating for human capital and lighter color). With a large enough sample size, such as that in the Add Health survey, genetic effects could be disentangled from shared family effects by comparing the association across sibling kinships. A shared family hypothesis predicts an equality of associations; more specifically, it predicts that the correlation within families will be zero and that this correlation will not vary by genetic relatedness. Alternatively, a genetic hypothesis predicts a near zero correlation between full siblings due to independent assortment and predicts a magnitude of a correlation no less than that between families between unrelated siblings. As can be seen above, the results above are equivocal. A statistically significant difference in the magnitude of the correlations was found between full and unrelated siblings but the full sibling correlation was positive, though not significantly so. Generally, the results are ambiguous because it was impossible to separate in the majority of instances full and half siblings.]
The pithy: correlation within families: zero — except between unrelated pairs. Correlation between families: weak, but significant or trending towards — and at a magnitude little different from that found in the whole sample. Too little power to establish a statistically significant difference between the correlations within and between families. N sib pairs (available)= ~200, N sin pairs (needed) = 500. Method, data source, and computations explained in the excel file below. I’ll work on Hispanics another time and then see if I can combine results to get the critical N. If anyone has advice on methodology, I’ll listen happily.
I’m leaving as pending — for now — the previous post on this.