The Bell Curve: Intelligence and Class Structure in American Life (122 page)

16
See references in Raschke 1987; South 1985.

17
Bronislaw Malinowski,
Sex, Culture, and Myth
(1930), quoted in Moynihan 1986,p. 170.

18
The production of illegitimate babies per unit population has also increased during this period, with the fastest growth occurring during the 1970s. In the jargon, the
rate
of illegitimate births has increased as well as the
ratio.
The distinction between rate and ratio raises a technical issue that has plagued the discussion of illegitimacy in recent years. Traditionally, illegitimacy rates have been computed by dividing the number of illegitimate births by the number of unmarried women. In a period when marital patterns are also shifting, this has the effect of confounding two different phenomena: the number of illegitimate births in the numerator of the ratio and the number of unmarried women in the denominator. To estimate the rate of change in the production of illegitimate children per unit population, it is essential to divide the number of illegitimate births by the entire population (or, if one prefers, by the number of women of childbearing age). This is almost never done, however, in nontechnical discussions (or in many of the technical ones, for that matter). For a discussion of the difference this makes in interpreting trends in illegitimacy, see Murray 1993.

19
Sweet and Bumpass 1987, p. 95. In 1960, there were 73,000 never-married mothers between the ages of 18 and 34; in 1980, there were 1,022,000.

20
Bachu 1991, Table 1. The figures for ages 18 to 34 are interpolated from the published figures for ages 15 to 34.

21
Not to mention that IQ has changed in the wrong direction to explain increasing illegitimacy (see the Flynn Effect, discussed in Chapters 13 and 15).

22
As in the case of school dropout, one may ask whether having a baby out of wedlock as a teenager caused school dropout, therefore resulting in an artificially low IQ score. As before, the cleanest way to test the hypothesis is to select all the women who had their first baby
after
they took the test in 1980 and repeat the analyses reported here, introducing a control for age at first birth. When this is done, the relationships reported continue to apply as strongly as, and in some cases more strongly than, they do for the entire sample.

A similar causal tangle is associated with the age at first birth. Age at first birth is a powerful explanatory variable in a statistical sense. It can drastically change the parameters, especially the importance of socioeconomic status and IQ, in a regression equation. But, in the 1990s, what causes a girl in her teens to have a baby? Probably the same things that might cause her to have an illegitimate baby: She grew up in a low-status household where having a baby young was an accepted thing to do; she is not very bright and gets pregnant inadvertently or because she has not thought through the consequences; or she is poor and has a baby because it offers better rewards than not having a baby, whether those rewards are tangible in the form of an income and apartment of her own through welfare, or in the form of having someone to love. And in fact all three variables—parental SES, IQ, and whether she was living in poverty prior to the birth—are powerful predictors of age at first birth, explaining 36 percent of the variance. Furthermore, age at first birth cannot be a cause of parental SES and poverty in the year prior to birth. Empirically, it can be demonstrated not to be a “cause” of the AFQT score, using the same logic applied to the case of illegitimacy.

23
Rindfuss et al. 1980.

24
Abrahamse et al. 1988. The analysis is based on a sample of 13,061 girls who were sophomores in 1980 at the time of the High School and Beyond (HS&B) baseline survey and also responded to the first follow-up questionnaire in 1982.

25
The exact figures, going from the bottom to the top quartile in socioeconomic status, are 38.7 percent, 29.7 percent, 19.9 percent, and 11.7 percent, based on weighted data, computed by the authors from the HS&B database. Figures reported here and on other occasions when we refer to the RAND study will sometimes show minor discrepancies with the published account, because Abrahamse et al. used imputed figures for certain variables, based on schoolwide measures, when individual data were missing. Our calculations do not use any imputed figures. As in the RAND study, all results are based on weighted analyses using the HS&B population weights.

26
For mothers of an illegitimate baby, the mean on the test of cognitive ability
was .73 SD below the mean for all girls who had babies, and .67 SD below the mean for all white girls (mothers and nonmothers).

27
Limiting the analysis to first births avoids a number of technical problems associated with differential number of children per woman by cognitive and socioeconomic class. Analyses based on all children born by the 1990 interview show essentially the same results, however. We also conducted a parallel set of analyses using as the dependent variable whether the woman had ever given birth to a child out of wedlock (thereby adding women without any children at all to the analysis). The interpretations of the results were not markedly different for any of the analyses presented in the text.

28
We are, as usual, comparing the effects of a shift equal to ±2 SDs around the mean for both independent variables, cognitive ability and socioeconomic status.

29
Bachu 1993, Table J.

30
Bachu 1993, Table J.

31
The comparable probabilities given parental SES standard scores of-2 and +2 were 31 percent and 19 percent.

32
The literature is extensive. Two recent reviews of the literature are Moffitt 1992 and Murray 1993. See also Murray 1994.

33
The writing on this topic is much more extensive for the black community than the white. See, for example, Anderson 1989; Duncan and Hoffman 1990; Furstenberg et al. 1987; Hogan and Kitagawa 1985; Lundberg and Plotnick 1990; Rowe and Rodgers 1992; Teachman 1985; Moffitt 1983.

34
For a detailed presentation of this argument, see Murray 1986b.

35
An analysis based not on the dichotomous variable, poverty, but on income had essentially the same outcome.

36
When we repeat the analysis yet again, adding in the presence of the biological father, these results are sustained. Poverty and cognitive ability remain as important as before; the parents’ poor socioeconomic status does not increase the chances of illegitimate babies.

1
Louchheim 1983, p. 175. See also Liebmann 1993.

2
Bane and Ellwood 1983; Ellwood 1986b; Hoffman 1987.

3
The studies are reviewed in Bendick and Cantu 1978.

4
Hopkins et al. 1987.

5
This figure includes women not reflected in the table who did not go on AFDC within the first year after birth, received welfare at some later date, but did not become chronic recipients.

6
In all cases, we limit the analysis to women for whom we have complete
data and whose child was born prior to January 1,1989. We also conducted this analysis with another definition of short-term recipiency, limiting the sample to women whose children had been born prior to 1986, divided into women who had never received welfare subsequently and women who had received welfare up to half of the years that they were observed but did not qualify as chronic welfare recipients. The results were similar to the ones reported in the text, with a large negative effect of IQ and an insignificant role for SES.

7
Bane and Ellwood 1983; Ellwood 1986a; Murray 1986a.

8
Ellwood 1986a; Murray 1986a.

9
We conducted a parallel analysis comparing chronic welfare recipients with all other mothers, including those who had been on welfare but did not qualify as chronic. There are no important differences in interpretation for the results of the two sets of analyses.

10
Among all white women, only 16 percent had not gotten a high school diploma, and 27 percent had achieved at least a bachelor’s degree.

11
Once again, this analysis has to be based on women with a high school diploma because there was no way to analyze welfare recipiency among white women with B.A.s. Only two white women with B.A.s in the NLSY had become chronic recipients. But for the high school graduates, the effect of parental SES is modest—slightly smaller than the independent effect of cognitive ability. This pattern was generally shared among women who had gone on to get their GED (recall that people with a GED are not included in the high school sample).

12
Some of the obvious explanations are not as important as one might expect. For example, most of the high school dropouts who became chronic welfare recipients were not poor; only 36 percent of them had been below the poverty line in the year before birth. Nor is it correct to assume that all of them had babies out of wedlock; nearly half (46 percent) of their first babies had been born within marriage. But 70 percent of the chronic welfare recipients among the high school dropouts had had their first child before they turned 19, which means that some very large proportion of them had the baby before they would normally have graduated. Among high school dropouts who had not had a child before their nineteenth birthday, the independent relationships of IQ and socioeconomic ststus shift back toward the familiar pattern, with the effects of IQ being much larger than those of socioeconomic status.

13
Indeed, the teenage mothers who did
not
become chronic welfare recipients had a slightly lower mean IQ than those who did (23d centile versus 26th centile). Meanwhile, the ones who did not become welfare recipients at all had a fractionally higher mean socioeconomic status than the ones who did (27th centile versus 26th).

14
Having a high school diploma was an important variable in all of the analyses of welfare, over and above the effects of either cognitive ability or socioeconomic background, and regarding either short-term or chronic welfare recipiency. The question is whether the high school diploma—and we are referring specifically to the high school diploma, not an equivalency degree—reflects a cause or a symptom. Does a high school education prepare the young woman for adulthood and the world of work, thereby tending to keep her off welfare? Or does the act of getting a high school diploma reflect the young woman’s persistence and ability to cope that tend to keep her off welfare? It is an important question; unfortunately, we were unable to think of a way to answer it with the data we have.

15
All are mutually exclusive groups. Criteria follow those for temporary and chronic welfare recipiency defined earlier.

1
Anderson 1936.

2
See Bronfenbrenner 1958, p. 424, for a review of the literature through the mid-1950s. For a recent empirical test, see Luster et al. 1989.

3
Kohn 1959.

4
Kohn 1959.

5
Kohn 1959, p. 366.

6
Heath 1983.

7
The study also includes “Trackton,” a black lower-class community.

8
Heath 1982, p. 54.

9
Heath 1981, p. 61.

10
Heath 1982, p. 62.

11
Heath 1982, p. 63.

12
Gottfried 1984, p. 330.

13
Kadushin 1988, p. 150.

14
Drawn from Kadushin, 1988, pp. 150-151. Formally, neglect is defined by one of the leading authorities, Norman Polansky, as a situation in which the caretaker “permits the child to experience avoidable present suffering and/or fails to provide one or more ingredients generally deemed essential for developing a person’s physical, intellectual or emotional capacities.” Quoted in Kadushin, p. 150.

15
Kaplun, 1976; Smith and Adler, 1991; Steele 1987; Trickett et al. 1991.

16
E.g., Azar et al. 1984. For a discussion of weaknesses in the state of knowledge about causes and an argument for continuing to treat abuse and neglect separately, see Cicchetti and Rizley 1981. See also Bousha and Twentyman 1984; Herrenkohl et al. 1983.

17
Some recent reviews of the evidence on causation are Hegar and Yung-man
1989; Polansky 1981; Zuravin 1989. The intergenerational explanation is one of the most widely known. For a review of the literature and some important qualifications to assumptions about intergenerational transmission, see Kaufman and Zigler 1987.

18
Besharov 1991.

19
D. Besharov and S. Besharov, quoted in Pelton 1978, p. 608.

20
Parke and Collmer 1975.

21
Coser 1965; Horowitz and Liebowitz 1969.

22
Jensen and Nicholas 1984; Osborne et al. 1988.

23
Leroy H. Pelton’s literature review is still excellent on the studies through the mid-1970s, as is Garbarino’s. See Garbarino and Crouter 1978; Pelton 1978. Also see Straus and Gelles 1986; Straus et al. 1980; Trickett et al. 1991. Unless otherwise noted, the literature review in this section is not restricted to whites.

24
U.S. Department of Health and Human Services 1988; Wolfe 1985.