Sixty-three percent of children who lived in poverty throughout the first three years had mothers in the bottom 20 percent of intelligence
Seventy-two percent of children in the bottom decile of IQ had mothers in the bottom 20 percent of intelligence
Ten percent of people scoring “yes” on the Middle Class Values index were in the bottom 20 percent of intelligence
The diminishing returns to coaching for the SAT
IQ gains attributable to the Consortium preschool projects
A half-century of Iowa tests: Improvement as the norm, the slump as a twelve-year aberration
Forty-one years of SAT scores
Among the most gifted students, there is good news about math, bad news about verbal
At selective schools, the median black edge was 180 SAT points, while Asians faced a median penalty of 30 points
When aggressive affirmative action began, black college enrollment surged for a decade
The student’s-eye-view of cognitive ability
The uncertain effects of affirmative action in the workplace
A revised view of equal employment opportunity after correcting for ethnic differences in the IQ distributions
In the 1970s, economic growth began to enlarge the affluent class
List of Tables
Overlap Across the Educational Partitions
The Validity of the GATB for Different Types of Jobs
The Validity of the AFQT for Military Training
The Role of g in Explaining Training Success for Various Military Specialties
The Validity of Some Different Predictors of Job Performance
Education, Experience, and Wages, 1979-1987
White Poverty by Parents’ Socioeconomic Class
White Poverty by Cognitive Class
Failure To Get a High School Education Among Whites
Which White Young Men Spent a Month or More Out of the Labor Force in 1989?
Job Disability Among Young White Males
Which White Young Men Spent a Month or More Unemployed in 1989?
Which Whites Get Married When?
Which Whites Get Divorced When?
The Incidence of Illegitimacy Among Young White Women
The Proportion of First Births That Are Illegitimate
Circumstances of the First Birth Among Whites
Which White Women Go on Welfare After the Birth of the First Child?
Educational Attainment of White Chronic Welfare Recipients
Low Birth Weight Among White Babies
Which White Children Grow Up in the Worst Homes?
Which White Toddlers Have the Worst Temperaments?
Which White Children Are Behind in Motor and Social Development?
Which White Children Have the Worst Behavioral Problems?
IQ in the Mother and the Child for Whites in the NLSY
Criminality and IQ Among White Males
The Odds of Getting Involved with the Police and Courts for Young White Males
The Odds of Doing Time for Young White Males
Whites and the Middle-Class Values Index
Reductions in the Black-White Difference on the National Assessment of Educational Progress
Black Wages As a Percentage of White Wages, 1989
Age at Childbearing
The Next Generation So Far, for Three Ethnic Groups in the NLSY
Ethnic Differences in Test Scores in Two Generations
Regression to the Mean and Ethnic Differences in Test Scores in Two Generations
IQ Equivalents for the Deciles
Prevalence of Low IQ Among Mothers of Children with Developmental Problems
What SAT Score Decline? The Results of the National Norm Studies, 1955-1983
Affirmative Action Weights: The Law School Aptitude Test
Affirmative Action Weights: The Medical College Admissions Test
Applicants to Graduate Schools
The Black-White IQ Difference by Job Category, 1990
Typical Results of State Teacher Competency Examinations
Job Performance of Black Affirmative Action Plumbers and Pipe Fitters Compared to White Regular Hires
A Note to the Reader
We have designed The Bell Curve to be read at several levels.
At the simplest level, it is only about thirty pages long. Each chapter except the Introduction and the final two chapters opens with a precis of the main findings and conclusions minus any evidence for them, written in an informal style free of technical terms. You can get a good idea of what we have to say by reading just those introductory essays.
The next level is the main text. It is accessible to anyone who enjoys reading, for example, the science section of the news magazines. No special knowledge is assumed; everything you need to know to follow all of the discussion is contained within the book. The main text does include considerable technical material, however. The documentation becomes especially extensive when we come to a topic so controversial that many readers will have a “This can’t possibly be true” reaction.
Sprinkled throughout the book are boxes that add more detail, discuss alternative ways of thinking about the data, or relate tidbits that don’t quite fit in the text. You may skip any of these without interrupting the flow of the narrative, but we think they add something (or they wouldn’t be there), and we encourage you to dip into them.
The endnotes provide the usual scholarly references. Some of them, indicated in text by endnote numbers enclosed in brackets, add short discussions that will be of interest mostly to specialists.
Finally, the appendixes elaborate on key issues. For example, readers who come to the book unfamiliar with statistics will find that Appendix 1 supplies the basics; if you want to know more about the debate over cultural bias in intelligence tests, Appendix 5 guides you through the literature on that issue; and so on. Other appendixes lay out the statistical detail that could not be fit into the main text and was too bulky for a note.
Regarding those pesky impersonal third-person singular pronouns and other occasions when the authors must assign a gender to a fictitious person used to illustrate a point, it seems to us there is a simple, fair solution, which we hereby endorse: Unless there are obvious reasons not to, use the gender of the first author. We use he throughout.
Preface
This book is about differences in intellectual capacity among people and groups and what those differences mean for America’s future. The relationships we will be discussing are among the most sensitive in contemporary America—so sensitive that hardly anyone writes or talks about them in public. It is not for lack of information, as you will see. On the contrary, knowledge about the connections between intelligence and American life has been accumulating for years, available in the journals held by any good university library and on the computer tapes and disks of public use databases.
People have shied from the topic for many reasons. Some think that the concept of intelligence has been proved a fraud. Others recall totalitarian eugenic schemes based on IQ scores or worry about such schemes arising once the subject breaks into the open. Many fear that discussing intelligence will promote racism.
The friends and colleagues whose concerns we take most seriously say something like this: “Yes, we acknowledge that intelligence is important and that people differ. But the United States is founded on the principle that people should be equal under the law. So what possible relevance can individual differences in intelligence have to public policy? What good can come of writing this book?” In answer, we ask these friends and you, the reader, to share for a moment our view of the situation, perhaps suppressing some doubts and assuming as true things that we will subsequently try to prove are true. Here is our story:
A great nation, founded on principles of individual liberty and self-government that constitute the crowning achievement of statecraft, approaches the end of the twentieth century. Equality of rights—another central principle—has been implanted
more deeply and more successfully than in any other society in history. Yet even as the principle of equal rights triumphs, strange things begin to happen to two small segments of the population.
In one segment, life gets better in many ways. The people in this group are welcomed at the best colleges, then at the best graduate and professional schools, regardless of their parents’ wealth. After they complete their education, they enter fulfilling and prestigious careers. Their incomes continue to rise even when income growth stagnates for everyone else. By their maturity, these fortunate ones commonly have six-figure incomes. Technology works in their behalf, expanding their options and their freedom, putting unprecedented resources at their command, enhancing their ability to do what they enjoy doing. And as these good things happen to them, they gravitate to one another, increasingly enabled by their affluence and by technology to work together and live in one another’s company—and in isolation from everybody else.
In the other group, life gets worse, and its members collect at the bottom of society. Poverty is severe, drugs and crime are rampant, and the traditional family all but disappears. Economic growth passes them by. Technology is not a partner in their lives but an electronic opiate. They live together in urban centers or scattered in rural backwaters, but their presence hovers over the other parts of town and countryside as well, creating fear and resentment in the rest of society that is seldom openly expressed but festers nonetheless.
Pressures from these contrasting movements at the opposite ends of society put terrific stress on the entire structure. The mass of the nation belongs to neither group, but their lives are increasingly shaped by the power of the fortunate few and the plight of the despairing few. The culture’s sense of what is right and wrong, virtuous and mean, attainable and unattainable—most important, its sense of how people are to live together—is altered in myriad ways. The fragile web of civility, mutual regard, and mutual obligations at the heart of any happy society begins to tear.
In trying to think through what is happening and why and in trying to understand thereby what ought to be done, the nation’s social scientists and journalists and politicians seek explanations. They examine changes in the economy, changes in demographics, changes in the culture. They propose solutions founded on better education, on more and better jobs, on specific social interventions. But they ignore an underlying element that has shaped the changes: human intelligence—the way it varies within the American population and its crucially changing role in our destinies during the last half of the twentieth century. To try to come to grips with the nation’s problems without understanding the role of intelligence is to see through a glass darkly indeed, to grope with symptoms instead of causes, to stumble into supposed remedies that have no chance of working.
We are not indifferent to the ways in which this book, wrongly construed, might do harm. We have worried about them from the day we set to work. But there can be no real progress in solving America’s social problems when they are as misperceived as they are today. What good can come of understanding the relationship of intelligence to social structure and public policy? Little good can come without it.
Acknowledgments
The first thing that made this book possible was our good fortune in being where we are—Harvard University and the American Enterprise Institute. Different as they are in many ways, these two splendid institutions gave us a gift that is too often taken for granted: freedom and support to pursue our inquiries wherever they took us.
For learned and often creative advice for dealing with methodological issues, our thanks go to James Heckman, Derek Neal, Robert Rosenthal, Donald Rubin, Christopher Winship, and the Harvard Psychology Department’s Seminar on the Analysis of Psychological Data. The staff of the Center for Human Resource Research—Paula Baker must be singled out—were unfailingly ready to answer our questions about the intricacies of the National Longitudinal Survey of Youth. In the world of psychometrics and testing, we benefited especially from the advice of Robert Forsyth, Arthur Jensen, Richard Lynn, Len Ramist, Malcolm Ree, and Frank Schmidt. Others who have read chapters or listened to us try to explain what we’re up to and then have offered advice, or at least raised their eyebrows usefully, are Douglas Besharov, Eileen Blumenthal, John Bunzel, John DiIulio, Christopher DeMuth, David Ellwood, Richard Epstein, Ronald Haskins, James Herrnstein, Karl Hess, Michael Horowitz, Fred Jewett, Michael Joyce, Cheryl Keller, Robert Klitgaard, Irving Kristol, Richard Larry, Marlyn Lewis, Glenn Loury, Harvey Mansfield, Frank Miele, Michael Novak, Warren Reed, Daniel Seligman, Irwin Stelzer, Joan Kennedy Taylor, Abigail Thernstrom, Daniel Vining, Dean Whitla, James Wilson, and Douwe Yntema. Along with some of those already mentioned, John Bishop, Philip Cook, George Borjas, Robert Frank, Sandra Scarr, and Richard Weinberg provided us with drafts of their ongoing work that filled in missing pieces of the puzzle.
We took unblushing advantage of the energy and good nature of research assistants, with Kris Kirby and Ira Carnahan taking on some huge tasks early in the work, followed by the invaluable help of Kristin Caplice, Joseph Fazioli, and one other who asked to remain anonymous out of his wish to preserve, as he put it, a viable political future.
All of these people, and others whom we have surely forgotten over the years, deserve our thanks for their help, but not the risk of being held accountable for what we’ve done with it.
We were lucky to have Erwin Glikes as our editor and Amanda Urban as our agent—the best in the business, and utterly undaunted by the hazards of this enterprise. The Bell Curve is Erwin’s title, and its manuscript was the last he completed editing before his death.
In a list of acknowledgments, we would be remiss not to mention each other. We decided to write this book in November of 1989, and since the spring of 1990 have been working at it nearly full time, for long stretches much more than full time, in continual collaboration. Our partnership has led to a more compelling intellectual adventure and a deeper friendship than we could have imagined. Authorship is alphabetical; the work was symbiotic.
At last, how shall we express our thanks to Susan Herrnstein and Catherine Cox? They could not be, and were not, overjoyed to see their husbands embark on a project as controversial as this one. But they have endured our preoccupation with the book and its intrusion into our families’ lives with love and humor. Beyond that, each of them read the entire manuscript, persuasively but affectionately pressing on us the benefit of their fine judgment, their good sense, and their honesty. In more ways than one, this book could not have been written without their help.
Richard J. Herrnstein
Charles Murray
3 June 1994
THE BELL CURVE
Introduction
That the word intelligence describes something real and that it varies from person to person is as universal and ancient as any understanding about the state of being human. Literate cultures everywhere and throughout history have had words for saying that some people are smarter than others. Given the survival value of intelligence, the concept must be still older than that. Gossip about who in the tribe is cleverest has probably been a topic of conversation around the fire since fires, and conversation, were invented.
Yet for the last thirty years, the concept of intelligence has been a pariah in the world of ideas. The attempt to measure it with tests has been variously dismissed as an artifact of racism, political reaction, statistical bungling, and scholarly fraud. Many of you have reached this page assuming that these accusations are proved. In such a context comes this book, blithely proceeding on the assumption that intelligence is a reasonably well-understood construct, measured with accuracy and fairness by any number of standardized mental tests. The rest of this book can be better followed if you first understand why we can hold such apparently heterodox views, and for this it is necessary to know something about the story of measured intelligence.
INTELLIGENCE ASCENDANT
Variation in intelligence became the subject of productive scientif
ic study in the last half of the nineteenth century, stimulated, like so many other intellectual developments of that era, by Charles Darwin’s theory of evolution. Darwin had asserted that the transmission of inherited intelligence was a key step in human evolution, driving our simian ancestors apart from the other apes. Sir Francis Galton, Darwin’s young cousin and already a celebrated geographer in his own right, seized on this idea and set out to demonstrate its continuing relevance by using the great families of Britain as a primary source of data. He presented evidence that intellectual capacity of various sorts ran in families in Hereditary Genius, published just a decade after the appearance of Origin of Species in 1859. So began a long and deeply controversial association between intelligence and heredity that remains with us today.1
Galton realized that he needed a precise, quantitative measure of the mental qualities he was trying to analyze, and thus he was led to put in formal terms what most people had always taken for granted: People vary in their intellectual abilities and the differences matter, to them personally and to society.2 Not only are some people smarter than others, said Galton, but each person’s pattern of intellectual abilities is unique. People differ in their talents, their intellectual strengths and weaknesses, their preferred forms of imagery, their mental vigor.
The Bell Curve: Intelligence and Class Structure in American Life Page 2
