A mixed electoral system is one that uses different electoral systems to fill different seats in a legislature. Most often, this involves a First Past the Post combined with a proportional component. The results of the combination may be mixed-member proportional (MMP), where the overall results of the elections are proportional, or mixed-member majoritarian, in which case the overall results are semi-proportional, retaining disproportionalities from the majoritarian component. Systems that use multiple types of combinations are sometimes called supermixed.
Mixed-member systems also often combine local representation (most often single-member constituencies) with regional or national (multi-member constituencies) representation, having multiple tiers. This also means voters often elect different types of representatives who might have different types of constituencies. Some representatives may be elected by personal elections where voters vote for candidates, and some by list elections where voters vote for electoral lists of parties.
In most mixed systems, every voter can influence both the district-based and PR aspects of an election, such as under parallel voting; however, some countries have multiple coexisting electoral systems that each apply to different voters.
Types of mixed systems
Compensatory/non-compensatory seat allocation A major distinction is often made between mixed compensatory systems and mixed non-compensatory systems. In both types of systems, one set of seats is allocated using a plurality or majoritarian method, usually first past the post. The remaining seats are allocated to political parties partially or wholly based on a proportional allocation method such as highest averages, largest remainder, or percentage pointsRing, Robert S. (2014) https://memorial.scholaris.ca/items/235236be-796a-48e4-9bc8-e4b200e6b844(thesis). Memorial University of Newfoundland.. The difference is whether or not the results of the district elections are considered when allocating the PR seats.
In mixed non-compensatory systems, such as parallel voting, the proportional allocation is performed independently of the district election component.
In mixed compensatory systems, the allocation of the top-up seats is done in such a way as to compensate as much as possible for dis-proportionality produced by the district elections. MMP generally produces proportional election outcomes, meaning that a political party that wins n percent of the vote will receive roughly n percent of the seats.
The following hypothetical example based on the one by Massicotte illustrates how "top-up" PR seats are typically allocated in a compensatory system and in a non-compensatory system. The example assumes a 200-seat legislative assembly where 100 seats are filled using FPTP and the other 100 seats are awarded to parties using a form of PR. The table below gives the popular vote and FPTP results. The number of PR seats allocated to each party depends on whether the system is compensatory or non-compensatory.
Party Popular vote FPTP seats PR seats Total seats (FPTP + PR)FPTP seats Party A 44% 64 ? ? Party B 40% 33 ? ? Party C 10% 0 ? ? Party D 6% 3 ? ? TOTAL 100% 100 100 200
In non compensatory system, each party wins its proportional share of the 100 PR seats. Under such a system, the total number of seats (FPTP + PR) received by each party would not be proportional to its share of the popular vote. Party A receives just slightly less of the popular vote than Party B, but receives significantly more seats. In addition to its success in the district contests, Party A receives almost as many of the PR seats as Party B.
Party Popular vote FPTP seats PR seats (non-compensatory) Total seats (FPTP + PR)PR seats (non-compensatory)Total seats (FPTP + PR) Party A 44% 64 44 108 (54% of assembly) Party B 40% 33 40 73 (36.5% of assembly) Party C 10% 0 10 10 (5% of assembly) Party D 6% 3 6 9 (4.5% of assembly) TOTAL 100% 100 100 200
If the PR seats are allocated in a compensatory system, the total number of seats awarded to each party is proportional to the party's share of the popular vote. Party B wins 33 of the district seats and its proportional share of the 200 seats being filled is 80 seats (40 percent of the total 200 seats) (the same as its share of the popular vote) so it is awarded 47 of the PR seats.
Party Popular vote FPTP seats PR seats (compensatory) Total seats (FPTP + PR)PR seats (compensatory)Total seats (FPTP + PR) Party A 44% 64 24 88 (44% of assembly) Party B 40% 33 47 80 (40% of assembly) Party C 10% 0 20 20 (10% of assembly) Party D 6% 3 9 12 (6% of assembly) TOTAL 100% 100 100 200
In practice, compensatory seat allocation is complicated by the possibility that one or more parties wins so many of the district seats ("overhang") that the available number of PR seats is insufficient to produce a fully proportional outcome. Some mixed compensatory systems have rules that address these situations by adding additional PR seats to achieve overall PR. These seats are used only until the next election, unless needed again at that time.
The two common ways compensation occurs are seat linkage compensation (or top-up) and vote linkage compensation (or vote transfer). Like a non-compensatory mixed system, a compensatory mixed system may be based on the mixed single vote (voters vote for a local candidate and that vote is used to set the party share of the popular vote for the party that the candidate belongs to) or it may be based on voters casting two separate votes.
Compensatory mixed systems single vote systems dual vote systems Seat linkage mixed single vote, top-up versions (MSV)
single vote (Lesotho) 50-point proportional representation (Proportional-first-past-the-post) Two vote "top-up" - broadly mixed-member proportional representation (MMP)
additional member system (AMS) alternative vote plus (AV+)Hybrids: e.g. parallel voting+seat linkage compensation (South Korea) Vote linkage positive vote transfer (PVT)
Hungary (local elections) Hybrids:
Parallel voting+PVT (Hungary) negative vote transfer/scorporo (Italy, 1993–2005)Others systems:dual-member proportional (DMP)mixed ballot transferable vote (MBTV)Non-compensatory mixed systemssingle vote systemsdual vote systemsNo linkage-parallel votingVote linkagemixed single vote, superposition Italian variant (Rosatellum)-Seat linkageList seats proportional to FPTP seats
Pakistan Bangladesh-
Types of combinations
Apart from the compensatory/non-compensatory typology, a more detailed classification is possible based on how component systems relate to each other, according to academic literature. Below is a table of different categories of mixed electoral systems based on the five main types identified by Massicotte & Blais. According to their terminology, methods of compensation are referred to as compensation is referred to as correction, while another type of dependent combination exists, called the conditional relation between sub-systems. Meanwhile, independent combinations mixed systems might have both local and national/regional tiers (called superposition), but some have only one at-large (national) tier, like the majority bonus system (fusion) or only a single tier for local/regional representation (called coexistence).
There are also supermixed systems, like rural-urban proportional (RUP), which is a hybrid mixed system that uses two tiers: the lower tier uses a proportional system, like list-PR or STV, in urban regions, and the upper tier uses MMP (itself a mixed system) either in rural regions alone or in all regions.
+CombinationTypeAttributesSystemExample(s) for useIndependent combinationFusionTwo formulas are used within each district (or one district for the whole electorate)Majority bonus (MBS)France (local), French PolynesiaCoexistence (hybrid)Different districts use different systems in one tiere.g. FPTP/SMP in single-member districts, list-PR in multi-member districts Democratic Republic of the Congo, PanamaSuperpositionDifferent tiers use different systemsParallel voting (e.g. FPTP/SMP locally, list-PR nationally)Lithuania, RussiaSingle vote mixed-member majoritarian (e.g. FPTP/SMP locally, list-PR nationally)Italy, PakistanDependent combinationCorrection (compensation)One formula uses the results of other to compensateSeat linkage mixed system with partial correction for overhang seats: New Zealand's mixed-member proportional representation (MMP)New ZealandSeat linkage mixed system with no correction for overhang seats: UK Additional member system (AMS) - a less proportional version of MMPScotlandSingle vote with seat linkage (for mixed-member proportional representation) 50-point proportional representation (correction via percentage points)Lesotho -Single vote with compensatory vote transfer (semi-proportional)Hungary (local)ConditionalOutcome of one formula determines the other formulae.g. conditional party block voting: party that receives more than 50%, gets all seats otherwise all seats distributed proportionally -Combination of combinationsSupermixedSuperposition + correctionScorporo / negative vote transfer (NVT), Parallel voting + PVTHungaryParallel voting + seat linkageSouth KoreaSuperposition + fusionNational plurality bonus in regional list-PRGreeceSuperposition + coexistencee.g. some elected by PR in single national district, some are elected locally by pluralityEcuadorCoexistence + conditionale.g. FPTP/SMP in single-member districts, conditional party block voting in multi-member districtsCameroon, ChadCoexistence + correctionRural-urban proportional representation (RUP)Denmark (formerly), Iceland (formerly)Conditional + correction + fusionMajority jackpot systems, particularly two-round variantsArmenia, San MarinoFusion + correctionDual-member proportional representation (DMP) - In a hybrid system, different electoral formulas are used in different contexts. These may be seen in coexistence, when different methods are used in different regions of a country, such as when FPTP is used in single-member districts and list-PR in multi-member districts, but every voter is a member of only one district (one tier). Some hybrid systems are generally not referred to as mixed systems, such as when as FPTP districts are the exception (e.g. overseas constituency) and list-PR is the rule, the overall system is usually considered proportional. Similarly, when FPTP is in single-member districts and used block voting (or party block voting) is used in multi-member districts, the system is referred to as a majoritarian one, as all components are majoritarian. Most mixed systems are not referred to as hybrid systems
Mixed-member majoritarian and mixed-member proportional
Another distinction of mixed electoral systems is between mixed-member proportional representation (MMP) and mixed-member majoritarian representation (MMM).
Parallel voting
Parallel voting is a mixed non-compensatory system with two tiers of representatives: a tier of single-member district representatives elected by a plurality/majoritarian method such as FPTP/SMP, and a tier of regional or at-large representatives elected by a separate proportional method such as party list PR. It is used for the first chamber (lower house) in many countries including Japan and Russia.
This type of parallel voting provides semi-proportional results, but is often referred to as mixed-member majoritarian representation, as the lack of compensation means each party can keep all the overhang seats it might win on the majoritarian side of the electoral system.
Seat linkage compensatory systems