The Diversity Index is a scale of 0 to 100 that represents the likelyhood that two persons, chosen at random from the same area, belong to different race or ethnic groups. If an area's entire population belongs to one race AND one ethnic group, then the area has zero diversity. An area's diversity index increases to 100 when the population is evenly divided into two or more race/ethnic groups.
| County | Diversity Index | |
|---|---|---|
| 1. | Mellette County | 58.0 |
| 2. | Jackson County | 57.6 |
| 3. | Bennett County | 57.1 |
| 4. | Lyman County | 55.1 |
| 5. | Charles Mix County | 54.4 |
| 6. | Roberts County | 53.8 |
| 7. | Corson County | 53.3 |
| 8. | Marshall County | 52.5 |
| 9. | Ziebach County | 49.4 |
| 10. | Beadle County | 47.5 |
| 11. | Dewey County | 45.5 |
| 12. | Minnehaha County | 41.8 |
| 13. | Pennington County | 40.4 |
| 14. | Moody County | 38.6 |
| 15. | Hughes County | 37.2 |
| 16. | Tripp County | 35.8 |
| 17. | Buffalo County | 35.5 |
| 18. | Walworth County | 34.1 |
| 19. | Fall River County | 31.8 |
| 20. | Brule County | 31.5 |
