This is a categorical variable that indicates the precise electoral formula used in an electoral tier.

1. Single-Member-District-Plurality (SMDP)
2. Two Round Majority-Plurality
3. Two Round Qualified Majority
4. Two Round Majority Runoff
5. Alternative Vote (AV)
6. Borda Count (BC)
7. Modified Borda Count (mBC)
8. Block Vote (BV)
9. Party Block Vote (PBV)
10. Limited Vote (LV)
11. Single Nontransferable Vote (SNTV)
12. Hare quota
13. Hare quota with largest remainders
14. Hare quota with highest average remainders
15. Hagenbach-Bischoff quota
16. Hagenbach-Bischoff quota with largest remainders
17. Hagenbach-Bischoff quota with highest average remainders
18. Droop quota
19. Droop quota with largest remainders
20. Droop quota with highest average remainders
21. Imperiali quota
22. Imperiali quota with largest remainders
23. Imperiali quota with highest average remainders
24. Reinforced Imperiali quota
25. D'Hondt
26. Sainte-Laguë
27. Modified Sainte-Laguë
28. Single Transferable Vote.

Note: Users can find a detailed description of the difference between types in the original codebook.