This book examines variation in the economicattainments of immigrants to the United States fromLatin America, relying primarily on data drawn fromthe 1990 census. The purpose is to explain asaccurately as possible why this variation occurs.Typically, researchers have chosen between twocompeting explanations. One, human capital theory,contends that variation in economic attainment is aproduct of different characteristics of individuals.The other, social capital theory, contends thatvariation in economic attainment is a product ofdifferences in characteristics of the societies fromwhich the workers come. The question is whether wemust choose one over the other. Given that boththeories have empirical support, the challenge is tobuild an appropriate methodology that allows us topartition the variation in economic attainments,identifying how much is explained by individual andhow much by group characteristics.