[In the following essay, Herrnstein and Murray contend that IQ test results are the most reliable predictor of socioeconomic success and failure in society.]

"But what about race?" we are asked whenever we try to talk about The Bell Curve. Part of the correct answer is that there are many interesting questions involving race and intelligence. Racial differences in means and distributions on IQ tests are a reality. As far as anyone can tell, they are not artifacts of test bias. Some of them call for a rethinking of policy, especially affirmative action. All of these topics are discussed at length in the book.

But another part of the correct answer to "What about race?" is that racial issues are secondary. People find it hard to accept this at face value. The topic of race and IQ, relegated to whispers for so many years, is in danger of becoming a test of one's intellectual machismo. If we try to talk about something else, many assume, it must be because we are afraid. So let us say it as loudly and clearly as the printed page permits: If tomorrow the U.S. consisted entirely of blue-eyed blonds, the crucial themes of The Bell Curve would remain unchanged. The increasing value of brains in the marketplace would remain. The driving role of cognitive stratification would remain. The prospects for a state in which high and moderate IQ taxpayers would become custodians of an underclass dominated by low IQ individuals would remain as grim—postponed for a few years, perhaps, if the nation consisted entirely of blue-eyed blonds, but no more than that.

Here is the reality: Approximately 75% of the American population still consists of whites of European origin. Within that non-Latino white population, here is what IQ means for the problems that are identified with the underclass:

The first lesson, drawn from a massive database known as the National Longitudinal Survey of Youth, is that low intelligence is a stronger precursor of poverty than low socioeconomic background. Or, to put it another way: If you have to choose, is it better to be born smart or rich? The answer is unequivocally "smart." A white youth who was reared in a home in which his parent or parents were chronically unemployed, worked at only menial jobs and had not gotten past the ninth grade, but who is himself of average intelligence—an IQ of 100—has nearly a 90% chance of being out of poverty by his early 30s. The high rates of poverty that afflict certain segments of the white population are determined more by intelligence than by socioeconomic background.

The correlation between IQ and employment patterns is also strong, with white males in the bottom 5% of IQ having three times the chance of being out of the labor force as men in the top 5%—after taking socioeconomic and educational background into account. Why are young men out of the labor force? One obvious possibility is physical disability. Yet here too cognitive ability is a strong predictor: Of the men who described themselves as being too disabled to work, more than nine out of 10 were in the bottom quarter of the IQ distribution.

Illegitimacy, one of the central social problems of the times, is also strongly related to intelligence. White women in the bottom 5% of the cognitive ability distribution are six times as likely to have an illegitimate first child as those in the top 5%. Is this really a hidden effect of poverty? On the contrary, the independent role of intelligence in predicting illegitimacy is higher among poor white women than among white women in general.

The odds that a white woman in the top 5% of IQ will go on welfare within a year of the birth of her first child is one in a hundred; for a white woman in the bottom 5%, it is better than one in two. White women who remain childless or have babies within marriage have a mean IQ of 105. Those who have an illegitimate baby but never go on welfare have a mean IQ of 98. Those who go on welfare but do not become chronic recipients have a mean IQ of 94. Those who become chronic welfare recipients have a mean IQ of 92.

Not surprisingly, there are other tragic correlations. For example, low IQ among white mothers is related to low birthweight for their children, even after controlling for socioeconomic background, poverty and age of the mother. Evaluations of child well-being reveal that, while high IQ is by no means a prerequisite for being a good mother, the disquieting finding is that the worst environments for raising children, of the kind that not even the most resilient children can easily overcome, are concentrated in homes in which the mothers are at the low end of the intelligence distribution.

The list of social pathologies linked with intelligence goes on. Consistent with a large scientific literature, white males in the National Longitudinal Survey of Youth who had been sentenced to a correctional institution as juveniles had a mean IQ of 93, compared with 106 for those who had never been stopped by the police. Once IQ is held constant, the relationship of socioeconomic background to juvenile delinquency among whites was nearly zero.

The steep increases in such things as illegitimacy, welfare dependency and crime during the past 30 years are obviously not to be explained by intelligence, which did not plummet during the same period. But things did happen which put people at the low end of the intelligence scale—white and black alike—at much greater risk of those bad things happening to them.

In this story, then, race plays a minor role. The forbidden tends to be fascinating by virtue of being forbidden, and so it has been with race and IQ. As with most forbidden things, the reality is not merely as exciting as imagination has made it. If one wants to understand the trajectory of American life, one must first inquire about the condition of and changes within white America. It is among whites at both extremes of the bell curve that the role of intelligence will play out decisively.