Many studies in economics and political science include the concept of ethnic diversity as a key independent variable in empirical studies. To date, however, only single-dimensional measures of ethnic diversity, such as ethnic fractionalization, have been available. In this paper, I define and measure three multidimensional characteristics of social structure—cross-cuttingness, cross-fractionalization, and subgroup fractionalization—and present a new cross-national data set comprised of indices along combinations of five cleavages: race, language, religion, region, and income. After addressing important definitional and measurement issues, I discuss the data and show how their inclusion in economic growth regressions reopens the theoretical debate regarding the influence of ethnic diversity, indicating the potential for these new indices to shed light on the role of ethnic diversity (and social structure more generally) with regards to a number of phenomena of concern to political scientists. The data set is publicly available from the Inter-University Consortium for Political and Social Research data archives and the Institute for Quantitative Social Science Dataverse Network.