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How does the Census Bureau measure racial and ethnic diversity?

While the concept of racial and ethnic composition refers to the racial and ethnic makeup of a population, the concept of diversity refers to the representation and relative size of different racial and ethnic groups within a population. Racial and ethnic diversity is maximized when all groups are represented in an area and have equal shares of the population.

We have used several approaches to measure the racial and ethnic diversity of the U.S. population in the 2020 Census results. These include the diversity index, prevalence rankings and diffusion score, and prevalence maps.

What are the limitations of these diversity measures?

A mathematical limitation of these diversity measures is that they require mutually exclusive or nonoverlapping race and Hispanic origin groups to calculate the diversity index. So in addition to the diversity index, we include other measures of diversity such as prevalence rankings, diffusion scores, and prevalence maps to illustrate the rich and complex racial and ethnic diversity of our nation’s population.

How is the diversity index meaningful for interpreting racial and ethnic data?

Diversity index illustrates the diversity of our nation, states, and counties. It provides a metric for understanding the heterogeneity of these communities, which can be analyzed over time. It also has a straightforward and consistent interpretation.

What are the key factors that contribute to increasing diversity?  

There are a number of reasons why the U.S. population is becoming more racially and ethnically diverse. For example, racial and ethnic differences in fertility, mortality, and migration (both domestic and international) can influence the composition of the population, making it more diverse over time. Trends in marriage and family formation also influence racial and ethnic diversity, as we have seen with increases in the multiracial population over the past several decades.