Horizontal inequality as an outcome

A considerable body of research suggests that horizontal inequality between ethnic groups has major socioeconomic implications, in particular for peace and economic development. Much of this work focuses on horizontal inequality as an independent causal variable, rather than an outcome of various processes. We offer conceptual, theoretical, and empirical reasons for treating horizontal inequality as an outcome and challenging assumptions of fixity. We first consider explanations for variation drawing on the literature on horizontal inequality, as well as on ethnicity more broadly. We then explore how horizontal inequality can be measured using survey and census data, and present analysis based on two datasets providing information on inequality in terms of educational attainment (HI-E) for the 1960s to 2000s. These data suggest both a general trend toward decline in HI-E over time and considerable regional variation. This article serves also to introduce and frame the contributions to this special section.