Cognitive ability has powerful, widespread and robust effects on social stratification: Evidence from the 1979 and 1997 US National Longitudinal Surveys of Youth

Few issues in the social sciences are as controversial as the role of cognitive ability for educational and subsequent socioeconomic attainments. There are a variety of arguments raised to dismiss, discount or discredit the role of cognitive ability: socioeconomic background is the dominant influence; if cognitive ability appears important, that is only because important predictors have been omitted; the relative importance of socioeconomic background and cognitive ability cannot be ascertained; and cognitive ability is simply a function of socioeconomic background and, for post-education socioeconomic attainments, education. This study analyses the effects of cognitive ability and socioeconomic background on a chronological sequence of social stratification outcomes - school grades, SAT and ACT scores, educational and occupational attainment, income and wealth - in data from the 1979 and 1997 National Longitudinal Surveys of Youth. The coefficients for cognitive ability decline marginally with the addition of socioeconomic background measures, including family-of-origin income averaged over several years, and wealth. In contrast, socioeconomic background coefficients decline substantially with the addition of cognitive ability. Net of educational attainment, cognitive ability has sizable effects on occupational attainment and income. Net of socioeconomic background, education and occupation, a one-standard-deviation difference in ability corresponds to a sizable 43% difference in positive wealth at around age 35 in the older cohort and a 25% increase in the younger cohort. Therefore, contrary to dominant narratives, cognitive ability is important to a range of social stratification outcomes, and its effects cannot be attributed to socioeconomic background or educational attainment.