Cognitive Partitioning by Occupation - The Emergence of a Cognitive Elite - The Bell Curve: Intelligence and Class Structure in American Life - Richard J. Herrnstein, Charles Murray

The Bell Curve: Intelligence and Class Structure in American Life - Richard J. Herrnstein, Charles Murray (1996)

Part I. The Emergence of a Cognitive Elite

Chapter 2. Cognitive Partitioning by Occupation

People in different jobs have different average IQs. Lawyers, for example, have higher IQs on the average than bus drivers. Whether they must have higher IQs than bus drivers is a topic we take up in detail in the next chapter. Here we start by noting simply that people from different ranges on the IQ scale end up in different jobs.

Whatever the reason for the link between IQ and occupation, it goes deep. If you want to guess an adult male’s job status, the results of his childhood IQ test help you as much as knowing how many years he went to school.

IQ becomes more important as the job gets intellectually tougher. To be able to dig a ditch, you need a strong back but not necessarily a high IQ score. To be a master carpenter, you need some higher degree of intelligence along with skill with your hands. To be a first-rate lawyer, you had better come from the upper end of the cognitive ability distribution. The same may be said of a handful of other occupations, such as accountants, engineers and architects, college teachers, dentists and physicians, mathematicians, and scientists. The mean IQ of people entering those fields is in the neighborhood of 120. In 1900, only one out of twenty people in the top 10 percent in intelligence were in any of these occupations, a figure that did not change much through 1940. But after 1940, more and more people with high IQs flowed into those jobs, and by 1990 the same handful of occupations employed about 25 percent of all the people in the top tenth of intelligence.

During the same period, IQ became more important for business executives. In 1900, the CEO of a large company was likely to be a WASP born into affluence. He may have been bright, but that was not mainly how he was chosen. Much was still the same as late as 1950. The next three decades saw a great social leveling, as the executive suites filled with bright people who could maximize corporate profits, and never mind if they came from the wrong side of the tracks or worshipped at a temple instead of a church. Meanwhile, the college degree became a requirement for many business positions, and graduate education went from a rarity to a commonplace among senior executives.

When one combines the people known to be in high-IQ professions with estimates of the numbers of business executives who are drawn from the top tenth in cognitive ability, the results do not leave much room for maneuver. The specific proportions are open to argument, but the main point seems beyond dispute: Even as recently as midcentury, America was still a society in which most bright people were scattered throughout the wide range of jobs. As the century draws to a close, a very high proportion of that same group is now concentrated within a few occupations that are highly screened for IQ.

Jobs sort people by their IQs, just as college does. But there is a difference between educational and occupational sorting. People spend only one to two decades in school. School may seem like forever when we are there, but we spend most of our lives with the sorting that centers on work and carries over into circles of friends and colleagues, and into communities—if not physically the same workplaces, communities, and friends throughout the life span, then generically similar ones. In this chapter, we continue our discussion of the contours of the intellectual landscape. An examination of occupational sorting will carry us through to the end of Part I.


No one decreed that occupations should sort us out by our cognitive abilities, and no one enforces the process. It goes on beneath the surface, guided by its own invisible hand. Testers observe that job status and intelligence test scores have gone together since there were intelligence tests to give.1 As tests evolved and as the measurement of status was formalized, studying the relation between the jobs and intelligence became a cottage industry for social scientists. By now, the relation has been confirmed many times, in many countries, and in many approaches to the data.2

This is not to say that the experts find nothing to quarrel about. The technical literature is replete with disagreement. Aside from the purely technical bones of contention, the experts argue about whether the IQ-job status connection is a by-product of a more fundamental link between educational level and job status. For example, it takes a law degree to be a lawyer, and it takes intelligence to get into and through law school, but aside from that, is there any good reason why lawyers need to have higher IQs on average than, say, bus drivers? At the height of egalitarianism in the 1970s, the received wisdom in many academic circles was “no,” with Christopher Jencks’s Inequality the accepted text.3 A related argument, stated forcefully by James Fallows, arises over whether an IQ score is a credential for certain jobs, like a union card for a musician, or whether there is a necessary link between job status and intelligence, like a good ear.4 By the time we get to the end of Part I, our answers to such questions should be clear. Here we review a few of the more illuminating findings, to push the discussion beyond the fact that occupational status is correlated with IQ.

One notable finding is that the correlation between IQ and job status is just about as high if the IQ test is given in childhood, decades before people enter the job market, as it is among young adults who are taking an intelligence test after years of education. For example, in a small but elegant longitudinal study of childhood intelligence and adult outcomes, the boys and girls in the sample were given IQ tests in childhood and then their job statuses and levels of schooling were measured on standard scales after they were at least 26 years old.5 The IQ scores they got when they were 7 or 8 years old were about as correlated with the status level of their adult jobs as their adult IQs would have been.6 Inasmuch as childhood IQ is more correlated with status than completed education, as it is in some studies, the thesis that IQ scores really just measure educational level is weakened.

Family members typically resemble each other in their occupational status.7 We are talking here not about a son or a niece or a brother-in-law going into the family business but about job status, however measured. On rating scales that categorize jobs from those with the highest status to those with the lowest, family members tend to land at similar levels. There are many exceptions; we all hear occasionally about families with several members who are doctors and lawyers plus another who is a blue-collar worker, or vice versa. But such stories call attention to themselves because they describe rarities. Mostly, relatives occupy neighboring, if not the same, rungs on the job status ladder, and the closer the relationship is, the nearer they are. Such commonplace findings have many possible explanations, but an obvious one that is not mentioned or tested often by social scientists is that since intelligence runs in families and intelligence predicts status, status must run in families. In fact, this explanation somehow manages to be both obvious and controversial.8

One useful study of family resemblance in status comes from Denmark and is based on several hundred men and women adopted in or around Copenhagen between 1924 and 1947.9 Four out of five of these adopted people had been placed with their adopting families in their first year of life; the average age of placement overall was 3 months. To all intents and purposes, then, the adoptees shared little common environment with their biological siblings, but they shared a home environment with their adoptive siblings. In adulthood, they were compared with both their biological siblings and their adoptive siblings, the idea being to see whether common genes or common home life determined where they landed on the occupational ladder. The biologically related siblings resembled each other in job status, even though they grew up in different homes. And among them, the full siblings had more similar job status than the half siblings. Meanwhile, adoptive siblings were not significantly correlated with each other in job status.10


The above comments apply to all sorts of occupations, from low status to high. But the relationship of IQ to occupations changes as the job becomes more cognitively demanding. Almost anyone can become a ditch digger (if he has a strong enough back); many can become cabinetmakers (if they have good enough small-motor skills), but only people from a fairly narrow range of cognitive ability can become lawyers. If lawyering pays more than cabinetmaking, what happens as the number of lawyering jobs increases, as it has in America? More people with high IQs are diverted to lawyering, which means that they are not going to become cabinetmakers or ditch diggers.

Now imagine that process writ large, and consider what has happened Within the handful of occupations that are most highly screened for IQ. We will concentrate here on a dozen such occupations, which we will refer to as “high-IQ professions.” Some of them have existed as long as IQ tests and are included in the list of occupations for the 1900 census: accountants, architects, chemists, college teachers, dentists, engineers, lawyers, and physicians. Others have emerged more recently or are relabeled in more recent occupational breakdowns: computer scientists, mathematicians, natural scientists, and social scientists.

The mean IQ of people entering those fields is about 120, give or take a few points.11 The state of knowledge is not perfect, and the sorting process is not precise. Different studies find slightly different means for these occupations, with some suggesting that physicians have a mean closer to 125, for example.12 Theoretical physicists probably average higher than natural scientists in general. Within each profession, the range of scores may be large. Even an occupation with a high mean may include individuals with modest scores; it will certainly include a sizable proportion below its mean—50 percent of them, if the distribution is symmetrical above and below its mean.13

Nonetheless, 120 is a good ballpark figure for estimating the mean person in these high-IQ professions, and it also has the advantage of marking the cutoff point for approximately the top tenth of the entire population in IQ.14Armed with this information plus a few conjectures, we may explore how cognitive stratification at the top of the American labor market has changed over the years. The figure below shows the answer for the twentieth century to date.

Once again, the portrait of American society depends on vantage point. Let us begin with the bottom line, showing the percentage of the entire labor force that is engaged in high-IQ professions. There has been a proportional increase during the twentieth century, but these people still constituted only about one out of fifteen Americans in the labor force as of 1990.

Now consider Americans in the top 10 percent (the top decile, in other words) in cognitive ability—everyone over the age of 25, including housewives, the retired, and others who are not counted as being part of the labor force. These people are represented by the middle line in the graph. In 1900, the number of jobs in the high-IQ professions soaked up only about one out of twenty of these talented people. By 1990, they soaked up almost five times as many, or one out of four.

Finally, consider the top line in the graph, which is limited to Americans who are in both the top decile of IQ and the labor force. In 1900, about one out of eleven was in one of the high-IQ professions; by 1990, more than one out of three. This still leaves almost two out of three of them unaccounted for, but we will get to them in the next section of the chapter.

The top IQ decile becomes rapidly more concentrated in high-IQ professions from 1940 onward


Source: U.S. Bureau of the Census 1975, Table D233—682; SAVS 1981, Table 675; U.S. Department of Labor, 1991, Table 22.

Note: Included are accountants, architects, chemists, college teachers, computer scientists, dentists, engineers, lawyers, mathematicians, natural scientists, physicians, and social scientists. Assumes 50 percent of persons in these professions have IQs of 120 or higher.

The specific proportions should be taken with a grain of salt, based, as they are, on estimates of IQs within the occupations. But we have a way of checking the 1990 estimate against actual experience, using the National Longitudinal Survey of Youth (described fully in the introduction to Part II), and our estimate fits quite closely.15 In any case, the basic trends are unmistakable. Unlike the steep slopes we saw for educational changes in the first half of the century, the high-IQ professions gained proportionally little of the working force through 1940. But after 1940, the trickle swelled to a flood, shown by the nonlinear upward sweep of the proportion in the top IQ decile who have more recently gone to work in this limited number of jobs.

The High-IQ Professions and the Cognitive Elite

We have been discussing the top decile: everyone with an IQ of 120 or higher. What about people in the even more rarefied cognitive elite, the top fraction of a centile who are so concentrated in a handful of universities during their college years? We have little to tell us exactly what is happening now, but we know what the situation was fifty years ago, through Lewis Terman’s famous study of 1,500 highly gifted children who were born in the early 1900s and followed throughout their lives. Their average IQs were over three standard deviations above the mean, meaning that the Terman sample represented about l/300th of the population. As of 1940, the members of the Terman sample who had finished their schooling were engaged in high-IQ professions at three times the rate of people in the top 10 percent—24 percent for the Terman sample against 8 percent for the top decile in 1940, as the preceding figure shows.16 If that was the case in 1940, when fewer than one in twelve people in the top decile were working in high-IQ professions, what might be the proportion for a comparable sample today? Presumably much higher, though how much higher is impossible to estimate with the available data.17


The changes in our twelve high-IQ professions understate how much occupational cognitive segregation there has been in this century. We lack data about other professions and occupations in which mean IQ may be comparably high (e.g., military officers, writers, journalists). But the biggest omission involves business executives. For while the mean IQ of all people who go into business cannot be near 120,18 both common sense and circumstantial evidence suggest that people who rise to the upper echelons of large businesses tend to have high IQs and that this tendency has increased during the course of the century.

One source of circumstantial evidence that ties success in major business to intelligence is the past and present level of education of business executives.19 In 1900, more than two-thirds of the presidents and chairmen of America’s largest corporations did not have even a college degree—not because many of them were poor (few had risen from out-right poverty) but because a college degree was not considered important for running a business.20 A Wall Street tycoon (himself a Harvard alumnus) writing in 1908 advised parents that “practical business is the best school and college” for their sons who sought a business career and that, indeed, a college education “is in many instances not only a hindrance, but absolutely fatal to success.”21

The lack of a college education does not mean that senior executives of 1900 were necessarily less bright than their counterparts in 1990. But other evidence points to a revolution in the recruitment of senior executives that was not much different from the revolution in educational stratification that began in the 1950s. In 1900, the CEO of a large company was likely to be the archetype of the privileged capitalist elite that C. Wright Mills described in The Power Elite: born into affluence, the son of a business executive or a professional person, not only a WASP but an Episcopalian WASP.22 In 1950, it was much the same. The fathers’ occupations were about the same as they had been in 1900, with over 70 percent having been business executives or professionals, and, while Protestantism was less overwhelmingly dominant than it had been in 1900, it remained the right religion, with Episcopalianism still being the rightest of all. Fewer CEOs in 1950 had been born into wealthy families (down from almost half in 1900 to about a third), but they were continuing to be drawn primarily from the economically comfortable part of the population. The proportion coming from poor families had not changed. Many CEOs in the first half of the century had their jobs because their family’s name was on the sign above the factory door; many had reached their eminent positions only because they did not have to compete against more able people who were excluded from the competition for lack of the right religion, skin color, national origin, or family connections.

In the next twenty-five years, the picture changed. The proportion of CEOs who came from wealthy families had dropped from almost half in 1900 and a third in 1950 to 5.5 percent by 1976.23 The CEO of 1976 was still disproportionately likely to be Episcopalian but much less so than in 1900—and by 1976 he was also disproportionately likely to be Jewish, unheard of in 1920 or earlier. In short, social and economic background was no longer nearly as important in 1976 as in the first half of the century. Educational level was becoming the high road to the executive suite at the same time that education was becoming more dependent on cognitive ability, as Chapter 1 showed. The figure above traces the change in highest educational attainment from 1900 to 1976 for CEOs of the largest U.S. companies.

In fifty years, the education of the typical CEO increases from high school to graduate school


Source: Burck 1976, p. 172; Newcomer 1955, Table 24.

The timing of the changes is instructive. The decline of the high school-educated chief executive was fairly steady throughout the period. College-educated CEOs surged into the executive suite in the 1925-1950 period. But as in the case of educational stratification, the most dramatic shift occurred after 1950, represented by the skyrocketing proportion of chief executives who had attended graduate school.24 By 1976, 40 percent of the Fortune 500 companies were headed by individuals whose background was in finance or law, fields of study that are highly screened for intelligence. So we are left with this conservative interpretation: Nobody knows what the IQ mean or distribution was for executives at the turn of the century, but it is clear that, as of the 1990s, the cognitive screens were up. How far up? The broad envelope of possibilities suggests that senior business executives soak up a large proportion of the top IQ decile who are not engaged in the dozen high-IQ professions. The constraints leave no other possibility. Here are the constraints and the arithmetic:

In 1990, the resident population ages 25 to 64 (the age group in which the vast majority of people working in high-IQ professions fall) consisted of 127 million people.25 By definition, the top IQ decile thus consisted of 12.7 million people. The labor force of persons aged 25 to 64 consisted of 100 million people. The smartest working-age people are disproportionately likely to be in the labor force (especially since career opportunities have opened up for women). As a working assumption, suppose that the labor force of 100 million included 11 million of the 12.7 million people in the top IQ decile.

We already know that 7.3 million people worked in the high-IQ professions that year and have reason to believe that about half of those (3.65 million) have IQs of 120 or more. Subtracting 3.65 million from 11 million leaves us with about 7.4 million people in the labor force with IQs of 120 or more unaccounted for. Meanwhile, 12.9 million people were classified in 1980 as working in executive, administrative, and managerial positions.26 A high proportion of people in those positions graduated from college, one screen. They have risen in the corporate hierarchy over the course of their careers, which is probably another screen for IQ. What is their mean IQ? There is no precise answer. Studies suggest that the mean for the job category including all white-collar and professionals is around 107, but that category is far broader than the one we have in mind. Moreover, the mean IQ of four-year college graduates in general was estimated at about 115 in 1972, and senior executives probably have a mean above that average.27

At this point, we are left with startlingly little room for maneuver. How many of those 12.9 million people in executive, administrative, and managerial positions have IQs above 120? Any plausible assumption digs deep into the 7.4 million people with IQs of 120 or more who are not already engaged in one of the other high-IQ professions and leaves us with an extremely high proportion of people of the labor force with IQs above 120 who are already working in a high-IQ profession or in an executive or managerial position. One could easily make a case that the figure is in the neighborhood of 70 to 80 percent.

Cognitive sorting has become highly efficient in the last half century, but has it really become that efficient? We cannot answer definitely yes, but it is difficult to work back through the logic and come up with good reasons for thinking that the estimates are far off the mark.

It is not profitable to push much further along this line because the uncertainties become too great, but the main point is solidly established in any case: In midcentury, America was still a society in which a large proportion of the top tenth of IQ, probably a majority, were scattered throughout the population, not working in a high-IQ profession and not in a managerial position. As the century draws to a close, some very high proportion of that same group is concentrated within those highly screened jobs.