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. | Buena Vista County | 68.2 |
| 2. | Crawford County | 64.9 |
| 3. | Woodbury County | 56.6 |
| 4. | Marshall County | 54.9 |
| 5. | Muscatine County | 50.2 |
| 6. | Polk County | 45.1 |
| 7. | Tama County | 44.6 |
| 8. | Louisa County | 44.1 |
| 9. | Johnson County | 43.5 |
| 10. | Scott County | 40.6 |
| 11. | Clarke County | 38.9 |
| 12. | Black Hawk County | 38.6 |
| 13. | Jefferson County | 38.3 |
| 14. | Wapello County | 37.0 |
| 15. | Wright County | 35.3 |
| 16. | Franklin County | 35.2 |
| 17. | Dallas County | 34.9 |
| 18. | Emmet County | 34.5 |
| 19. | Sioux County | 34.5 |
| 20. | Story County | 34.0 |
