The Bell Curve: Intelligence and Class Structure in American Life
Page 18
Specialists who have followed these figures know that this explanation is misleading.15 Poverty among children has always been much higher in families headed by a single woman, whether she is divorced or never married. For families headed by a single woman, the poverty rate in 1991 was 36 percent; for all other American families, 6 percent.16 Indeed, the national poverty rate for households headed by a single woman has been above 30 percent since official poverty figures began to be available in 1959.17 The equation is brutally simple: The higher the proportion of children who live in households headed by single women, then, ceteris paribus, the higher the proportion of children who will live in poverty. An important part of the increasing child poverty in the United States is owed to the increasing proportion of children who live in those families.18 The political left and right differ in their views of what policies to follow in response to this state of affairs, but recently they have broadly agreed on the joint roles of gender and changes in family structure in pushing up the figures for child poverty.
Poverty Among Children: The Role of the Mother’s IQ
What does IQ add to this picture? It allows us to focus sharply on who is poor and why, and to dispense with a number of mistaken ideas. To see how, let us consider women, and specifically women with children.19 Here is the graph that results when we ask how often mothers with differing IQs and differing family structures suffer from poverty. (In the figure, the effects of the mothers’ socioeconomic background are held constant, as are the number of children, which is factored into the calculation of the poverty line.)
The first, glaring point of the figure is that marriage is a powerful poverty preventive, and this is true for women even of modest cognitive ability. A married white woman with children who is markedly below average in cognitive ability—at the 16th centile, say, one standard deviation below the mean—from an average socioeconomic background had only a 10 percent probability of poverty.
The role of the mother’s IQ in determining which white children are poor
Notes: For computing the plot, age and SES were set at their mean values.
The second point of the graph is that to be without a husband in the house is to run a high risk of poverty, even if the woman was raised in an average socioeconomic background. Such a woman, with even an average IQ, ran a 33 percent chance of being in poverty. If she was unlucky enough to have an IQ of only 85, she had more than a 50 percent chance—five times as high as the risk faced by a married woman of identical IQ and socioeconomic background. Even a woman with a conspicuously high IQ of 130 (two standard deviations above the mean) was predicted to have a poverty rate of 10 percent if she was a single mother, which is quite high compared to white women in general. Perhaps surprisingly, it did not make much difference which of the three kinds of “nonmarriage”—separation, divorce, or no marriage at all—was involved. The results for all three groups of women were drastically different from the results for married women, and quite similar to each other (which is why they are grouped in the figure.)
The third obvious conclusion is that IQ is extremely important in determining poverty among women without a husband present. A poverty rate of 10 percent for women with IQs of 130 may be high compared to some standards, but it is tiny compared to the steeply rising probabilities of poverty that characterize women with below average cognitive ability.
Poverty Among Children: The Role of the Mother’s Socioeconomic Background
Now we pursue the same issue but in terms of socioeconomic background. Remember that the steep downward curve in the figure above for unmarried mothers is the effect of IQ after holding the effects of socioeconomic status constant. What is the role of socioeconomic background after we take IQ into account? Not much, as the next figure shows.
We used the same scale on the vertical axis in both of the preceding graphs to make the comparison with IQ easier. The conclusion is that no matter how rich and well educated the parents of the mother might have been, a separated, divorced, or never-married white woman with children and an average IQ was still looking at nearly a 30 percent chance of being below the poverty line, far above the usual level for whites and far above the level facing a woman of average socioeconomic background but superior IQ. We cannot even be sure that higher socioeconomic background reduces the poverty rate at all for unmarried women after the contribution of IQ has been extracted; the downward slope of the line plotted in the graph does not approach statistical significance.20
The role of the mother’s socioeconomic background in determining which white children are poor
Note: For computing the plot, age and IQ were set at their mean values.
There are few clearer arguments for bringing cognitive ability into the analysis of social problems. Consider the hundreds of articles written about poverty among children and about the effects of single-parent families on poverty. Of course, these are important factors: Children are more often poor than adults. Family breakup is responsible for a major portion of the increase in child poverty. But if analysts are trying to understand the high rates of poverty among children, it must be done against the background that whatever other factors increase the risk of poverty among unmarried mothers, they hit unmarried mothers at low levels of intelligence much harder than they do those at high levels of intelligence—even after socioeconomic background is held constant.
HOLDING BOTH COMPLICATIONS AND POLICY THOUGHTS AT BAY
You have been following a common process in social science. An initially simple issue becomes successively more complicated. And we have barely gotten started—an analysis in a technical journal seldom has as few independent variables as the ones we have examined. For that matter, even this simplified analysis represents only the end result of a long process. In the attached note, we describe how big the rest of the iceberg is.21
Complex analysis has both merits and faults. The merit is that the complications are part of reality. Einstein’s injunction that solutions should be as simple as possible, but no simpler, still applies. At the same time, social science often seems more in need of the inverse injunction, to introduce as much complexity as necessary, but no more. Complications can make us forget what we were trying to understand in the first place. Here is where we believe the situation stands:
By complicating the picture, we raise additional questions: Education is important in affecting poverty; the appropriate next step is to explore how intelligence and socioeconomic status are related to years of education. Marriage is important in determining poverty; we should explore how intelligence and socioeconomic status are related to marriage. These things we shall do in subsequent chapters.
But the simple picture, with only IQ, parental SES, and age in the equation, restricted to our all-white sample, continues to tell a story of its own. A major theme in the public dialogue in the United States has been that socioeconomic disadvantage is the primary driving force behind poverty. The simple picture shows that it just isn’t so for whites.22 The high rates of poverty that afflict certain segments of the white population are determined more by intelligence than by socioeconomic background. The force and relevance of this statement does not seem to us diminished by the complications it does not embrace.
Indeed, now that we are returning to basics, let us remember something else that could be overlooked in the welter of regression analyses. The poverty rate for whites in Class V was 30 percent—a percentage usually associated with poverty in poor urban neighborhoods. Ethnically and culturally, these are supposed to be the advantaged Americans: whites of European descent. But they have one big thing working against them: they are not very smart.
Like many other disabilities, low intelligence is not the fault of the individual. Everything we know about the causes of cognitive ability, genetic and environmental, tells us that by the time people grow to an age at which they can be considered responsible moral agents, their IQ is fairly well set. Many readers will find that, before writing another word, we have already made the case
for sweeping policy changes meant to rectify what can only be interpreted as a palpably unfair result.
And yet between this and the chapters that will explore those policy issues stretch a few hundred pages of intervening analysis. There is a reason for them. By adding poverty to the portrait of cognitive stratification described in Part I, we hope to have set the terms of a larger problem than income inequality. The issue is not simply how people who are poor through no fault of their own can be made not poor but how we—all of us, of all abilities and income levels—can live together in a society in which all of us can pursue happiness. Changing policy in ways that affect poverty rates may well be part of that solution. But as we observed at the outset of the chapter, poverty itself has been declining as various discontents have been rising during this century, and curing poverty is not necessarily going to do much to cure the other pains that afflict American society. This chapter’s analysis should establish that the traditional socioeconomic analysis of the origins of poverty is inadequate and that intelligence plays a crucial role. We are just at the beginning of understanding how intelligence interacts with the other problems in America’s crisis.
Chapter 6
Schooling
Leaving school before getting a high school diploma in the old days was usually not a sign of failure. The youngster had not dropped out but simply moved on. As late as 1940, fewer than half of 18-year-olds got a high school diploma. But in the postwar era, the high school diploma became the norm. Now, not having one is a social disability of some gravity.
The usual picture of high school dropouts focuses on their socioeconomic circumstances. It is true that most of them are from poor families, but the relationship of socioeconomics to school dropout is not simple. Among whites, almost no one with an IQ in the top quarter of the distribution fails to get a high school education, no matter how poor their families. Dropout is extremely rare throughout the upper half of the IQ distribution. Socioeconomic background has its most powerful effect at the lowest end of the social spectrum, among students who are already below average in intelligence. Being poor has a small effect on dropping out of school independent of IQ; it has a sizable independent effect on whether a person finishes school with a regular diploma or a high school equivalency certificate.
To raise the chances of getting a college degree, it helps to be in the upper half of the distribution for either IQ or socioeconomic status. But the advantage of a high IQ outweighs that of high status. Similarly, the disadvantage of a low IQ outweighs that of low status. Youngsters from poor backgrounds with high IQs are likely to get through college these days, but those with low IQs, even if they come from well-to-do backgrounds, are not.
Of all the social behaviors that might be linked to cognitive ability, school dropout prior to high school graduation is the most obvious. Low intelligence is one of the best predictors of school failure, and students who fail a grade or two are likely to have the least attachment to school And yet this relationship, as strong as it is now, is also new. The very concept of school failure is a modern invention. In the era of the one-room schoolhouse, students advanced at their own pace. There were no formal grade levels, no promotions to the next grade, hence no way to fail.1
“Dropping out” is an even more recent concept, created by the assumption that it is normal to remain in school through age 17. Until recently, it wasn’t typical. In 1900, the high school diploma was the preserve of a tiny minority of American youth: The number of those who got one amounted to only 6 percent of the crop of potential seniors that year. This figure, known as the graduation ratio, is calculated as the percentage of the 17-year-old population.2 Perhaps even more startling, it was not until the beginning of World War II that the graduation ratio first passed the 50 percent mark. The figure shows the story from 1900 to 1990.3
The trendlines that overlie the data indicate two broad phases in this ninety-year history. The first phase, from 1908 until the early 1920s, featured moderate expansion of high school education. It did not appear moderate at the time—the graduation rate more than doubled from 1900 to 1922—but the growth was nonetheless moderate by comparison with steep surge from 1922 until the beginning of World War II. This was the opening of the second growth phase, which lasted, with an interruption for World War II, until 1964. The story since 1964 has been mixed. Graduation rates stalled during the last half of the 1960s and then reversed during the 1970s. The trend since 1980 has been uncertainly and shallowly upward. As of 1992, the graduation ratio for 17-year-olds stood at 76 percent, near the 1969 high of 77 percent. The proportion of people who eventually graduate or get a high school equivalency certificate now stands at about 86 percent for the population as a whole.4
In the first half of the century, the high school diploma becomes the norm
Source: DES 1992, Table 95; U.S. Bureau of the Census, 1975, Table H598-601.
Americans today take it for granted that the goal is to graduate everyone and that a high school dropout rate is a social evil. But earlier thinkers, even those in our liberal tradition, were dubious about educating the entire population beyond the rudiments of literacy. Voltaire’s view that “the lower classes should be guided, not educated,” was typical until this century.5 Even early in this century, many observers feared that unqualified youngsters were being educated beyond their abilities. “We must turn back the clock,” one prominent educator wrote in 1936, “to take some five million boys and girls from the educational dole.”6
And yet when the psychometricians sought to document the fear that the country was trying to educate the ineducable, they found little evidence for it. One investigator, Frank Finch, assembled all of the competent studies of the intelligence of high school students conducted from 1916 (the earliest study he could find) to 1942. The mean IQ of ninth graders in these studies was 105; the mean IQ of the twelfth graders or graduates was 107, trivially different.7 The data suggest that the large number of youngsters who dropped out between ninth grade and high school graduation averaged less than 105 in IQ, but not by much (a calculation explained in the note).8
Finch found no increasing trend over time in the IQ gap between dropouts and graduates during the early part of the century. Replicating the story that we described regarding the college level in Chapter 1, the first decades of the century saw American high school education mushroom in size without having to dip much deeper into the intellectual pool. This process could not go on forever. As the high school diploma became the norm, the dropouts were likely to become more self-selected for low IQ, and so indeed it transpired.
We have not been able to determine exactly when the gap between nongraduates and graduates began to open up. Probably it was widening even by the early 1940s. By the early 1950s, a study in Iowa found a ten-point gap in IQ between dropouts and high school graduates.9 Another study, in 1949, of 2,600 students who had been given an IQ test in the seventh grade, found a gap between the graduates and nongraduates of about thirteen IQ points, close to the IQ’s standard deviation of fifteen.10 The proportion of students getting a high school diploma had reached about 55 percent by then. By the spring of 1960, when 70 percent of students were graduating, the data from Project TALENT—the large, nationally representative sample of high school students mentioned in Chapter 1—indicate a gap equivalent to almost sixteen IQ points between the academic aptitude of those who graduated and those who did not, slightly more than a standard deviation.11 This is tantamount to saying that the average dropout had an IQ that put him at the 15th centile of those who graduated.
The situation seems to have remained roughly the same since then. By the standard current definition of the population that “gets a high school education”—meaning either a diploma or by passing an equivalency examination—the NLSY data reveal that the mean score of those who get a high school education is 1.28 standard deviations higher than those who do not. Comparing those who get the ordinary high school diploma with all those who left high school before doing so (inclu
ding those who later get an equivalency certificate), the gap is 1.02 standard deviations.
WHITE HIGH SCHOOL DROPOUT IN THE NLSY
Who drops out of high school these days? The following table shows the story for NLSY whites in the various cognitive classes. The results could hardly be starker. Among whites in the top quartile (Classes I and II together), virtually everyone got a high school education. In the bottom quartile of the IQ distribution (Classes IV and V together), 39 percent of whites did not.12 This huge discrepancy is also predictable, however, given the close relationship between IQ and educational attainment—so predictable that we should pause for a moment before viewing dropout rates with alarm. Is a 39 percent dropout rate for students in the lowest quartile of IQ “high”? From one perspective, it seems so, considering how essential education appears to be for making a living. From another perspective, it is remarkable that over 60 percent of white youths with IQs under 90 did get a high school education. It is particularly remarkable that nearly half of the youths in Class V, with IQs of 75 and under, completed a high school education, despite being on the borderline (or beyond) of the clinical definition of retarded.13 Whether these figures say something about the ability of low-IQ students to learn or about the state of American secondary education is a topic we defer until Chapter 18.
Failure to Get a High School Education Among Whites