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. | Rosebud County | 58.6 |
| 2. | Big Horn County | 57.4 |
| 3. | Lake County | 55.7 |
| 4. | Blaine County | 55.4 |
| 5. | Roosevelt County | 52.5 |
| 6. | Glacier County | 51.8 |
| 7. | Hill County | 49.6 |
| 8. | Chouteau County | 38.8 |
| 9. | Phillips County | 33.9 |
| 10. | Pondera County | 33.9 |
| 11. | Cascade County | 32.4 |
| 12. | Yellowstone County | 31.3 |
| 13. | Valley County | 30.3 |
| 14. | Toole County | 29.3 |
| 15. | Richland County | 25.7 |
| 16. | Silver Bow County | 24.3 |
| 17. | Powell County | 24.1 |
| 18. | Missoula County | 23.4 |
| 19. | Deer Lodge County | 23.2 |
| 20. | Beaverhead County | 22.9 |
