A Note on the Use and Misuse of the Racial Diversity Index



This note concerns the use of the Blau index of racial and ethnic diversity in the social sciences and in policy analysis. The diversity index, by design, captures the heterogeneity of the population group being studied, typically according to the racial and ethnic categories of the U.S. Census but does not account for the relative size of specific racial groups. Thus, with the most commonly used diversity index, the implicit assumption is that for the purposes of the analysis a population that is 80 percent white and 20 percent Asian is identical to a population that is 80 percent black and 20 percent Hispanic. Examples are given from studies of voting behavior, organizational performance, and the provision of public goods and services to show that the diversity index is often used in ways that are inappropriate given the context of the study.