Bell Curve

Notes to pages 493-501 76313. The assumptions used for the figure are extremely conservative. Most ohviously,the standard deviation of 15 is too high. People within an occupationalcategory will always tend to have a smaller dispersion than thegeneral population. If we change nothing except reduce the standard deviationsto 12 for both blacks and whites, in line with the observed standarddeviations in the NLSY, the black-white ratios rise from 1.7(professional-technical) and 1.6 (clerical) to 2.5 and 1.9 respectively. Inaddition, however, the graph on page 490 is conservative in using an IQrange that encompasses 90 percent of the white workers in an occupationalcategory. The lower the bottom end of the range is, the more it Jisproportionatelyinflates the eligible portion of the black population (changes inthe top end of the range are at the tail of the distrihution and add very littleto the eligible pool). Visualize the hell curve: By lowering the bottomcutoff for professional-technical professions from 100 to 98 (for example),everyone in that very fat part of the curve is treated as being just as cligiblefor a professional-technical occupation as anyone else--even though,in reality, they are much less likely than persons with higher 1Qs to getsuch jobs. If, for example, we base the range on the IQs that ernhrace 80percent of the white workers in an occupation-more realistic in many respects-theblack-white ratio in 1990 grows to 2.3 for professionaltechnicaloccupations and 1.8 for clerical. Rut the conclusions still holdeven if we broaden the range still further than in the graph, to ernhrace 95percent of all people in those occupations. In that case-which assumes,implausibly, that all people with IQs higher than 89.8 are equally likely tc\be hired for technical-professional johs and that all people with IQs hetween82.0 and 130.3 are equally likely to be hired for clerical johs-theblack-white ratio as of 1990 is still greater than 1 in both instances: 1 .,? forprofessional-technical, 1.5 for clerical. In short, the differences producedby altering the assumptions can make substantial differences in the si:e ofthe estimates ofdisproportionate hiring, but even assumptions that go wellbeyond common sense and the available data do not change the overallconclusions drawn in the text.14. The observations using the CPS and the NLSY are not completely independent,insofar as we took our estimate of the IQ range for clerical andprofessional-technical occupations from the data on NLSY whites. Rutthose parameters did not constrain the results for blacks.15. The sample in these analyses excluded persons who were still in school in1990.16. Jaynes and Williams 1989, Tables 4-1,6-1.17. Hartigan and Wigdor 1989. See also Chapters 3 and 13.18. As of 1987, states had such a certification process. See Rudner 1988.19. Straus and Sawyer 1986.20. Lerner 1991.21. In Pennsylvania, with the highest pass rates, the state commissioner ofhigher education openly acknowledged that Pennsylvania sought to avoidlawsuits alleging racial bias in the test by establishing a low cutoff scorethat they would subsequently try to raise. See H. Collins, "Minority groupsare still lagging on teacher's exam," Philadelphia Inquirer, Aug. 5, 1989, p.B1.22. The answer to the question of how such large differences can show up inotherwise credentialed teachers is, in effect, the topic of the precedingchapter, on affirmative action in higher education.23. If we make the empirically more likely assumption that IQ does have a positivecorrelation with the nonintellectual skills, then the people with lowintellectual skills will, on average, also have depressed nonintellectual jobskills.24. For examples of affirmative action programs in public bureaucracies, seeLynch 1991, pp. 24-32; Taylor 1992, Chaps. 4,5.25. Carlson 1993.26. Carlson 1993, p. 28.27. Carlson 1993, p. 30.28. Washington Post, October 24-28, 1993.29. Delattre 1989; Sechrest and Bums 1992.30. Among the other stories we have located linking poor worker performanceto hiring under affirmative action requirements are one reporting an increasein collisions and other accidents on the New York public transportationsystem (K. Foran, "TA lax on Safety," Newsday, Sept. 19, 1990,p. 5), another describing the rise in criminal behavior among Detroit's policeofficers (E. Salholz, "Going After Detroit's rogue cops," Newsweek,Sept. 5, 1988, p. 37), and one discussing the much higher rate of firingsamong Boston's black postal workers, compared to white workers (B.McAllister, "Researchers say Postal Service tried to block article on fir.ings," Washington Post, Oct. 17, 1992, p. A3).31. Silberberg 1985. See also Ford et al. 1986; Kraiger and Ford 1985.32. Silherherg has his own interesting hypotheses about these differences,which we do not elaborate here. Nothing in his account is at variance withour conclusion that affirmative action procedures are exacting a cost inworker performance.33. Hacker 1992, p. 25.34. In fact, that was pecisely the excuse often given by the major leagues fornot hiring blacks.35. For a detailed statement of this perspective, see Kelman 1991.36. Quoted in Bolick 1988, p. 49. See also Taylor 1992, p. 126.37. There is a presumption that if we cannot explain a group difference, it is