The social context of g
The only commentator who brings Spearman’s hypothesis directly and specifically into apposition with its real-life social and economic consequences, is Cattell, who predicts that the percentage of blacks in different occupations should be inversely related to the mean intelligence levels of persons employed in the occupations. If shown to be true, this prediction would mean, of course, that disparities in the proportional representation of black and white workers in various occupational categories are not mainly attributable to prejudice and discrimination in hiring, but are due to differences in measurable g-loaded abilities, whatever the cause of the differences. I have not looked into data on this point myself, but quite precise data on a range of occupations (ranging from physician and engineer to truck driver and meat cutter), directly aimed at Cattell’s prediction, have been assembled by Linda Gottfredson (personal communication), a sociologist at the Johns Hopkins University. In light of Cattell’s query, it would be most valuable if Gottfredson submitted this analysis to Continuing Commentary. Gottfredson’s analysis, based on 1970 and 1980 statistics from the U. S. Department of Labor and the Bureau of the Census, strikingly bears out Cattell’s prediction, with a near perfect rank-order correlation between the theoretically expected and the observed ratios of black to white employees in different occupations.

Differences in the Distribution of G and Its Effect on Culture: The USA as a Case

Galton introduced a biometric approach to studying human populations. It was the foundation on which Spearman, Eysenck, and other staunch empiricists would erect the London School of Psychology’s biological approach to psychology. All were keenly interested in, not just the structure of intelligence, but also how its distribution within populations affects national well-being (e.g., Eysenck, 1973), including the mental distance between individuals, social cohesion, cultural level and social habits, diffusion of information («percolation range»), rate of innovation, proneness to extreme (simplistic) political positions, and economic divergence (Cattell, 1938). Drawing on these mechanisms, I look at how policies to achieve occupational parity, in spite of persistently large racial differences.

Data are publicly available in the United States for (a) number of black and white males employed in detailed occupations, (b) the ranges of IQ from which various occupations recruit their workers (recruitment ranges), and (c) the IQ distributions of blacks and whites. Thirty years ago (Gottfredson, 1986), I used these data to estimate whether black males were employed at the same rate as white males in 1970 and 1980 when they fall within the recruitment ranges. I examined 9 large occupations (physician, engineer, secondary teacher, real estate sales, fire fighter, police officer, electrician, truck driver, and butcher/meat cutter) falling in four IQ recruitment ranges (86–112, 91–117, 109–134, and 114+). Here I update those analyses with employment data for 1990 and 2005–2009.
Employment trends:
• If black and white males were recruited from the same IQ ranges, we would expect the B/W ratio of %-of-blacks to %-of-whites in an occupation to rise from .05 (physicians, engineers) to .72 (truck drivers, meat cutters).
• In 1970 and 1980, the B/W ratios for actual employment were more consistent with black males being recruited from .5 SD below that for white males (.22 to 1.07).
• The B/W ratios for actual employment rose in 1990 and 2005–2009; half were commensurate with black males being recruited from 1 SD below white males. Cultural trends: More blacks in good jobs and elite schools; working class white males have worse health and job prospects; institutions restructured; race relations worse; political discontent.

Human variation in intelligence is a biological fact that poses social challenges, especially when identifiable groups differ noticeably in mental ability. How a culture reacts to that variation also shapes its future. A nation that ignores or denies the practical and social significance of substantial intelligence differences risks its well-being. Constructive alternatives are available.

• Cattell, R. B. (1938). Some changes in social life in a community with a falling intelligence quotient. The British Journal of Psychology, 28, part 4, 430–450.
• Eysenck, H. J. (1973). The inequality of man. London: Temple Smith.
• Gottfredson, L.S. (1986). Societal consequences of the g factor in employment. Journal of Vocational Behavior, 29, 379-410.