Education, Income, and Ability

Abstract

Current estimates of the contribution of education to economic growth have been questioned because they ignore the interaction of education with ability. Whether the neglect of ability differences in the analyses of the income-education relationship results in estimates that are too high was considered in an earlier paper by one of the authors (Griliches 1970), and a negative answer was conjectured. In this paper, we pursue this question a bit further, using a new and larger body of data. Unfortunately, a definitive answer to this question is hampered both by the vagueness and elasticity of "education" and "ability" as analytical concepts and by the lack of data on early (preschooling) intelligence. The data examined in this paper are based on a 1964 sample of U.S. military veterans. The variables measured include scores on a mental ability test, indicators of parental status, region of residence while growing up, school years completed before service, and school years completed during or after service. These have allowed us to inquire into the separate effects of parental background, intelligence, and schooling. The basic problem and analytical framework can be set out very simply. Let income be a linear function of education and ability, or, Y a + P1E + P(2G + u, where Y is income, E is education, G is ability,