An electoral system (or voting system) is a set of rules that determine how elections and referendums are conducted and how their results are determined.
Some electoral systems elect a single winner (single candidate or option), while others elect multiple winners, such as members of parliament or boards of directors.
The study of formally defined electoral methods is called social choice theory or voting theory, and this study can take place within the field of political science, economics, or mathematics, and specifically within the subfields of game theory and mechanism design.
Name(s) | Variations | Type of representation | Mixed? | Single/multi-winner | List / candidate-based system | Type of decision rule | Type of ballot | Number of votes / voter | Number of tiers
(if mixed) |
---|---|---|---|---|---|---|---|---|---|
First-past-the-post (FPTP/FPP)[1] Single-member plurality (SMP/SMDP) |
two-round system with lower than 50% requirement in first round | majoritarian | No | single-winner | candidate | plurality | single choice | 1 | N/A |
General ticket
Party-block voting (PBV) |
majoritarian | No | multi-winner | list | plurality | single choice | 1 | N/A | |
Plurality block voting (BV)
plurality-at-large voting (multiple non-transferable vote, MTNV) |
limited party block voting | majoritarian | No | multi-winner | candidate | plurality | multiple choice | =number of winners | N/A |
Limited voting (LV)
limited block voting partial block voting (multiple non-transferable vote, MNTV) |
limited party block voting | semi-proportional | No | multi-winner | candidate | plurality | multiple choice | <number of winners | N/A |
Single non-transferable vote (SNTV) | semi-proportional | No | multi-winner | candidate | plurality | single choice | 1 | N/A | |
Single transferable vote (STV)
Hare–Clark electoral system[2] (proportional ranked-choice voting)[3] |
semi-proportional / proportional | No | multi-winner | candidate | quota | ranked choice (ordinal voting) | 1 (effectively) | N/A | |
Instant-runoff voting (IRV)[4]
(Alternative vote - AV)[5] (Ranked-choice voting - RCV)[6] (Single-transferable vote - STV) (Hare's method)[7] |
contingent vote,
supplementary vote, Coombs' method |
majoritarian | No | single-winner | candidate | majority | ranked choice (ordinal voting) | 1 (effectively) | N/A |
Two-round system (TRS)[8]
Runoff voting |
Non-partisan primary,
multi-round voting |
majoritarian | No | single-winner | candidate | majority | single choice | 1 (each round) | N/A |
Two-round block voting
(majority block voting)(multiple non-transferable vote, MNTV) |
majoritarian | No | multi-winner | candidate | majority | multiple choice | =number of winners (each round) | N/A | |
Multiple transferable vote (MTV)
(Preferential block voting) |
majoritarian | No | multi-winner | candidate | majority | ranked choice (ordinal voting) | =number of winners, effectively | N/A | |
Exhaustive ballot | majoritarian | No | single-winner /multi-winner | candidate | majority | single choice | 1 | N/A | |
Cumulative voting | panachage (certain types) | majoritarian / semi-proportional | No | single-winner /multi-winner | candidate | plurality | cumulative ballot | >1 | N/A |
Approval voting (AV)[9] | block approval voting | majoritarian | No | single-winner /multi-winner | candidate | plurality | multiple choice | any number
(max. one for one candidate) |
N/A |
Score voting Range voting |
Approval voting (score voting 0-1) | majoritarian / semi-proportional | No | single-winner /multi-winner | candidate | plurality | score ballot(cardinal voting) | N/A | |
Borda count | majoritarian / semi-proportional | No | single-winner /multi-winner | candidate | plurality | ranked choice (ordinal voting) | N/A | ||
Condorcet method | Copeland's method,
Dodgson's method, Kemeny–Young method, Minimax, Nanson's method, ranked pairs, Schulze method, Tideman's alternative methods |
majoritarian | No | single-winner | candidate | majority against every candidate | ranked choice (ordinal voting) | N/A | |
Party-list proportional representation
list-PR |
Largest remainderHighest averagesBinomial voting | semi-proportional / proportional | No | multi-winner | list (+ candidate, if open list) | quota or divisor method | single choice | 1 (effectively) | N/A |
Superposition - non-compensatory combination of FPTP + List-PR
(Supplementary member system) |
Two-round system + List-PR
mixed single vote version |
semi-proportional | Yes | multi-winner(+ single-winner in districts) | candidate + list | mixed non-compensatory | single choice | 2 (each tier) | 2 |
Seat-linkage compensatory combination of FPTP + List-PR | mixed single vote versionbest-loser mixed-member proportional | semi-proportional / proportional | Yes | multi-winner(+ single-winner in districts) | candidate + list | mixed compensatory | single choice | 2 (each tier) | 2 |
Vote-linkage compensatory combination of FPTP + List-PR
Positive vote transfer system (PVT)[12] (mixed single vote - MSV[13]) (Additional member system - AMS) |
negative vote transfer | semi-proportional / proportional | Yes | multi-winner(+ single-winner in districts) | candidate + list | mixed compensatory | single choice | 1 | 2 |
Dual member proportional (DMP)[14] | semi-proportional / proportional | Yes | multi-winner | list or candidate | plurality | single choice | 1 | 1 |
Electoral system for national legislatures
(lower house or unicameral) |
---|
Majoritarian representation (winner-take-all) Semi-proportional representation (non-mixed) No election (e.g. Monarchy)
|
Original source: https://en.wikipedia.org/wiki/List of electoral systems.
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