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. | Philadelphia County | 78.3 |
| 2. | Lehigh County | 75.0 |
| 3. | Monroe County | 68.8 |
| 4. | Berks County | 68.2 |
| 5. | Dauphin County | 67.2 |
| 6. | Delaware County | 60.1 |
| 7. | Luzerne County | 60.1 |
| 8. | Northampton County | 59.2 |
| 9. | Montgomery County | 53.5 |
| 10. | Lebanon County | 51.6 |
| 11. | Pike County | 50.8 |
| 12. | Chester County | 50.3 |
| 13. | Lancaster County | 47.9 |
| 14. | York County | 47.2 |
| 15. | Lackawanna County | 47.1 |
| 16. | Forest County | 45.8 |
| 17. | Allegheny County | 45.3 |
| 18. | Bucks County | 42.5 |
| 19. | Cumberland County | 42.1 |
| 20. | Erie County | 39.3 |