DORI Index: Measuring Diversity in Representative Institutions

How diverse are political institutions? Despite the theoretical and political relevance of this question, there is no standard measure of diversity in political institutions, limiting systematic research on diversity of representation. To address this gap, I introduce the Diversity of Representation Index (DORI), a multidimensional metric that quantifies diversity within political institutions by considering the variety and balance of represented groups and the proportionality of their representation relative to their population size—i.e., their descriptive representation. Using examples from national parliaments in Canada and Germany, and data on the presence of women and African Americans in all 50 U.S. state legislatures and their populations from 2009 to 2021, I illustrate DORI's application and properties. I demonstrate the significance of assessing diversity and explore its implications for policy outcomes. DORI offers a valuable tool for representation studies, enabling empirical analysis of the multidimensional nature of political representation.