About

The Racial Diversity measures the changing racial and ethnic composition in an area or neighborhood over time. According to the 2020 U.S. Census, nationally, the three most prevalent groups were the same for the total, under-18, and 18-and-over populations: 1) The White alone, non-Hispanic population was the largest or most prevalent race or ethnic group, 2) The Hispanic or Latino population was the second-most prevalent race or ethnic group, and 3) The Black or African American alone, non-Hispanic population was the third-most prevalent race or ethnic group ¹. While the White (non-Hispanic) group remains the largest racial group in most counties, racial and ethnic diversity varies significantly across U.S. counties, with the highest diversity among children in counties located in the West, South, and parts of the Northeast. Many of these counties—particularly in California, Texas, Florida, and New York—show a greater mix of racial and ethnic groups among youth compared to adults.

Why is the Racial Diversity important to the Structural Racism and Discrimination (SRD) Index?

Understanding change in the racially diversifying neighborhoods can explain specific forms of inequality and inequity ². For example, uneven access to institutional and economic resources often coincides with the uneven spatial distribution of racial groups across neighborhoods ³, as does exposure to crime, pollution, and racial health disparities ^4,5. Residents of diverse neighborhoods experience more casual interracial contact, which tends to dampen negative stereotyping and lower exposure to racism and discrimination and perceived threat of outgroups ⁶. 

What is the expected relation to Structural Racism and Discrimination?

A higher value of racial diversity in a county contributes to a higher value or score of the SRD index.

How is the Racial Diversity calculated?

Data Source

We obtained data from the IPUMS National Historical Geographic Information System (NHGIS) ⁷. The data is publicly available.

Data

We used the following four variables at the county level.

Variables*	Year	Unit
Total Population by County	1990 | 2000 | 2010 | 2020	Number
Black or African American alone population	1990 | 2000 | 2010 | 2020	Number
White alone population	1990 | 2000 | 2010 | 2020	Number
Other race (American Indian and Alaska Native alone, Asian alone, Native Hawaiian and Other Pacific Islander alone, Some Other Race alone, and Two or More Races population)	1990 | 2000 | 2010 | 2020	Number

* Individuals from both Hispanic and non-Hispanic ethnicities are included.

Methodology

We calculated the Racial Diversity in a county using the Entropy index (E) ⁸. The entropy index shows the degree of evenness in the size of different racial-ethnic populations, which make up the total population (of all ages) of the county. Entropy or E is calculated as follows. We used three races: White, Black, and Other
$$
E = \sum_{r=1}^{R} P_r \ln\left(\frac{1}{P_r}\right)
$$

Where:
Pr: Proportion of population by race in the given county
r: race. We used three races: White, Black, and Other (refer to the table above for the races included in Other)
R = 3; for three races

The formula sets the maximum value of E to the natural log of the number of groups. Thus, the maximum entropy in our analysis of three broad racial groups is ln(3) = 1.099. Such a value would occur only when all groups are of equal size (i.e., each racial group constitutes one-quarter of the population). At the opposite extreme, an E value of zero signifies complete homogeneity or no diversity, with all population members in the same group (e.g., an all-white neighborhood). We standardize E by dividing it by its three-group maximum and multiplying by 100, thereby setting its range of possible values from zero to 100.

Missing Data

We have 13 counties with no data in 2020, and none for the 2010, 2000, and 1990 years.

References

1. Menchaca, A., Pratt, B., Jensen, E., & Jones, N. (2023, May 22). Examining the racial and ethnic diversity of adults and children. U.S. Census Bureau. https://www.census.gov/library/stories/2023/05/racial-and-ethnic-diversity-of-adults-and-children.html

2. Farrell, C. R., & Lee, B. A. (2011). Racial diversity and change in metropolitan neighborhoods. Social Science Research, 40(4), 1108-1123.

3. Eric Oliver, J., & Wong, J. (2003). Intergroup prejudice in multiethnic settings. American journal of political science, 47(4), 567-582.

4. Acevedo-Garcia, D., Osypuk, T. L., McArdle, N., & Williams, D. R. (2008). Toward a policy-relevant analysis of geographic and racial/ethnic disparities in child health. Health affairs, 27(2), 321-333.

5. Fitzpatrick, K., & LaGory, M. (2002). Unhealthy places: The ecology of risk in the urban landscape. Routledge.

6. Eric Oliver, J., & Wong, J. (2003). Intergroup prejudice in multiethnic settings. American journal of political science, 47(4), 567-582.

7. Manson, S., Schroeder, J., Van Riper, D., Knowles, K., Kugler, T., Roberts, F., & Ruggles, S. (2024). IPUMS National Historical Geographic Information System: Version 19.0 [Dataset]. IPUMS.

8. Farrell, C. R., & Lee, B. A. (2011). Racial diversity and change in metropolitan neighborhoods. Social Science Research, 40(4), 1108-1123.