Case Study Four: Socioeconomic Status

Parental socioeconomic status is a long-standing sociological concept but, at the same time, it is necessarily a construct. It isn't a tangible, inarguable quantity, like height and weight. Herrnstein and Murray get their measure of socioeconomic status by averaging four factors at equal weight: mother's education, father's education, father's occupation, and family income. The last two of these were missing for many of the National Longitudinal Study of Youth subjects, and in those cases, Herrnstein and Murray substituted an average for the entire sample. This tends to overstate the socioeconomic status of those people, and therefore to reduce its impact, relative to IQ, in the authors' calculations.

Michael Hout of the University of California at Berkeley, along with five colleagues, recalculated the effect of socioeconomic status, using the same variables but weighting them differently. They write: "We find that socioeconomic background affects poverty far more than Herrnstein and Murray claimed. Our estimate of the effect of socioeconomic background on whites' risk of being in poverty in 1990 is 66 per cent higher than theirs; our estimate for African Americans is 53 per cent higher than theirs."

In another calculation, Hout and his colleagues found that if you correct IQ scores to eliminate the effect of education, Herrnstein and Murray's estimates of the ability of IQ to predict poverty can be made to look dramatically overstated--by 61 percent for whites and 74 percent for blacks. In other words, according to Hout et al., Herrnstein and Murray's key finding that IQ predicts poverty much better than socioeconomic status does is substantially a result of the way they handled the statistics.

In a reply to critics published in Commentary in May 1995--before Hout and his colleagues had published, but after several other scholars had complained about the measure of socioeconomic status used in The Bell Curve--Murray wrote that he and Herrnstein had simply used "the same elements everybody else uses" to construct their measure, and that "there is no way to construct a measure of socioeconomic background using the accepted constituent variables that makes much difference in the independent role of IQ." This last is precisely what the Hout team says it has done. Finally, Murray called for the whole concept of socioeconomic status to be discarded as useless "as a way of interpreting social problems," because IQ is so much more important. (It's a good thing this hadn't happened before The Bell Curve was published, since the centerpiece of Herrnstein and Murray's analysis is comparing its effect to that of IQ.)

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