Semi-proportional representation characterizes multi-winner electoral systems which allow some representation of smaller parties or candidates, but produce results that do not always reflect the strength of the competing political forces in a way that is proportional to the shares of the votes they receive. Semi-proportional voting systems are between proportional systems like party-list proportional representation or single transferable vote and winner-take-all systems. Examples of semi-proportional systems include the single non-transferable vote, limited voting, and parallel voting.
There are different measures of proportionality, and no objective threshold, so opinions differ on what constitutes a semi-proportional system, a non-proportional system and a proportional system.
Single-vote systems
Semi-proportional systems Election systems in which a party can achieve its due share of seats (proportionality) only by coordinating its voters are usually considered to be semi-proportional. They are not non-proportional or majoritarian, since in the perfect case the outcome will be proportional and in many cases it is close to proportional, but they are not universally proportional either, since the perfect case is not guaranteed without coordination. Such systems include the single non-transferable vote and cumulative voting, both of which are commonly used to elect a range of members based on party identification) and achieve approximately-proportional outcomes while maintaining simplicity and reducing the cost of election administration. Under these systems, parties may coordinate voters by limiting the size of the party slate or by using complex vote management schemes where voters are asked to randomize which candidate(s) they support or vote in specified ways, such as through differently-worded voting cards.
These systems are notable for the absence of an ordered party list. Candidates may coordinate their campaigns, and present or be presented as agents of a party, but voters may choose to support one candidate among the said group but not the others (that is, panachage is permitted).
Single transferable vote
Some writers consider the single transferable vote to be semi-proportional because of its favoritism towards major parties, sometimes caused by a combination of the Droop quota in small districts, as well as the vote management that may be involved when optional preferential voting is used, producing exhausted ballots. On the other hand, some describe it as proportional on the grounds that it is proportional in the limit of infinitely-large constituencies.David M. Farrell, Electoral Systems (2011) However, on party basis, if first preferences are used as guide, STV is only proportional for solid coalitions, if voters rank candidates along party lines and no significant number of votes cross party lines. The proportionality of STV, as measured by first preferences, breaks down if voters are split across party lines or choose to mark preferences candidates of different parties. Under STV, each elected member is elected by the exact same number of votes (the quota) or something very close to it, so proportionality is produced that way.
Other Other forms of semi-proportional representation are based on, or at least use, party lists to work. Looking to the electoral systems effectively in use around the world, there are three general methods to reinforce the winner-take-all principle of representation (but not necessarily majoritarianism or majority rule, see electoral inversion and plurality) starting from basic PR mechanisms: parallel voting, the majority bonus system (MBS), and extremely reduced constituency magnitude.
In additional member systems (AMS), the number of additional members may not be sufficient to balance the disproportionality of the original system, thereby producing less than proportional results. When this imbalance is created intentionally, the result could be described as a semi-proportional system — for example, in the Welsh Senedd, where only 33.3% of members are compensatory. The electoral system commonly referred to in Britain as the "additional member system" is also used for the Scottish Parliament and the London Assembly, with generally proportional results. Similarly, in vote transfer based mixed single vote systems, the number of compensatory seats may be too low (or too high) to achieve proportionality. Such a system is used in Hungary in local elections. The "scorporo" system used for the Parliament of Italy from 1993 to 2005 and the electoral system for the National Assembly of Hungary since 1990 are also special cases, based on parallel voting, but also including compensatory mechanisms – which however are insufficient for providing proportional results.
A majority bonus system takes an otherwise proportional system based on multi-member constituencies, and introduces disproportionality by granting additional seats to the first party or alliance. Majority bonuses help produce landslide victories similar to those which occur in elections under plurality systems. The majority bonus system was first introduced by Benito Mussolini to win the election of 1924. It has remained in use in Italy, as well as seeing some use in San Marino, Greece, and France.
The simplest mechanism to reinforce major parties in PR system is to severely restrict the number of seats per electoral district, which increases the Droop quota (the number of votes needed to be guaranteed a seat).
The last main group usually considered semi-proportional consists of parallel voting models. The system used for the Chamber of Deputies of Mexico since 1996 is considered a parallel voting system, modified by a list-seat ceiling (8%) for over-representation of parties.
Semi-proportional electoral systems can increase political polarization.
Usage
CountryLegislative bodyLatest election (year)Type of majoritarian system(Seats per constituency)Electoral systemTotal seatsGovernmental systemNotesAndorraGeneral Council2018 Mixed-member majoritarian2 (local districts) / 14 (nationwide constituency)Parallel voting / superposition (MMM): Party block voting (PBV) locally + list PR nationwide28Parliamentary systemDemocratic Republic of the CongoNational Assembly2018 Mixed-member majoritarian1–17Coexistence mixed majoritarian (MMM): First-past-the-post (FPTP/SMP) in single-member districts and List PR in multi-member districts (Largest remainder)500DjiboutiNational Assembly2018 Mixed-member majoritarian3–28Fusion / majority jackpot (MBS): 80% of seats (rounded to the nearest integer) in each constituency are awarded to the party receiving the most votes (party block voting), remaining seats are allocated proportionally to other parties receiving over 10% (closed list, D'Hondt method)65Presidential systemFranceFrench Polynesia Assembly2018 Mixed-member majoritarian4–17Two-round majority bonus system (MBS) in multi-member constituencies57GeorgiaParliament2020 Mixed-member majoritarian1 (local districts), 120 (national constituency)Parallel voting / superposition (MMM): Party-list PR (closed list) + First-past-the-post (FPTP/SMP)150Parliamentary systemGreece Mixed-member majoritarianMajority bonus system (MBS)GuineaNational Assembly2020 Mixed-member majoritarian1 (local districts), 76 (national constituency)Parallel voting / superposition (MMM): Party-list PR (Hare quota) + First-past-the-post (FPTP/SMP)114HungaryNational Assembly (Országgyűlés)2018 Mixed-member majoritarian1 (local districts), 93 (national constituency)Supermixed / Mixed-member majoritarian (MMM): First-past-the-post (FPTP/SMP) + national list-PR for 93 seats (combination of parallel voting and positive vote transfer)199Parliamentary systemBefore the 2014, a different mixed system was used with a two-round system in single-member districtsIraqSingle non-transferable vote (SNTV)ItalyChamber of Deputies2018 Mixed-member majoritarian1 (local districts), 12 (Italians abroad constituency), ?-? (multi-member districts)Superposition / Mixed-member majoritarian (MMM) using a single vote List PR + First-past-the-post (FPTP/SMP)630Parliamentary systemSenate2018 Mixed-member majoritarian1 (local districts), 6 (Italians abroad constituency), ?-? (multi-member districts)Superposition / Mixed-member majoritarian (MMM) using a single vote List PR + First-past-the-post (FPTP/SMP)315Parliamentary systemRepublic of Korea (South Korea)National Assembly2020 Mixed-member majoritarian1 (local districts), 17 supplementary seats (parallel voting), 30 additional seats (AMS),Supermixed / Mixed-member majoritarian (MMM): First-past-the-post (FPTP/SMP) and List PR (hybrid of parallel voting and AMS)300Presidential systemKuwaitSingle non-transferable vote (SNTV)KyrgyzstanSupreme Council2021 Mixed-member majoritarian1 (local districts), 54 (nationwide constituency)Parallel voting / superposition (MMM): Party-list PR (open list) + First-past-the-post (FPTP/SMP)90Presidential systemLithuaniaSeimas2020 Mixed-member majoritarian1 (local districts), 70 (nationwide constituency)Parallel voting / superposition (MMM): Two-round system (TRS) for 71 seats + List PR (Largest remainder) for 70 seats141Semi-presidential systemMadagascarNational Assembly2019 Mixed-member majoritarian1–2Coexistence: First-past-the-post (FPTP/SMP) in 87 single-member districts, party-list PR (Closed list, highest averages method) in 32 two-member districts (64 seats in binomial system)151Semi-presidential systemMauritaniaNational Assembly2018 Mixed-member majoritarian1–3 (local districts), 40 (nationwide constituency)Coexistence+superposition (parallel) supermixed/hybrid: Two-round system (TRS) in single-member districts, two-round block voting (BV) in dual-member districts, and List PR (simple quota largest remainder; closed-list) in larger districts + twice 20 nationally List PR (one set of 20 reserved for women)157Semi-presidential systemMonacoNational Council2018 Mixed-member majoritarian24 (nationwide constituency)Superposition / Mixed-member majoritarian (MMM) using a single (panachage) ballot: Plurality block voting (BV) in single nationwide constituency for 16 seats; D'Hondt method (8 seats)24Parliamentary system PalestineLegislative Council2006 Mixed-member majoritarian1–9 (local districts), 66 (nationwide constituency)Parallel voting / superposition (MMM): First-past-the-post (FPTP/SMP) in single-member districts and Plurality block voting (BV) in two-seat districts for 66 seats in total (some reserved for Christians) + List PR for 66 seats132Semi-presidential systemIn the 1996 elections, 88 PLC members were chosen from several multi-member constituencies via block votingPanamaNational Assembly2019 Mixed-member majoritarianCoexistence mixed majoritarian (MMM): First-past-the-post (FPTP/SMP) in single-member districts, Saripolo or Sartori method (Largest remainder, but remainders only for those with no seats) in multi-member districts71Presidential systemPhilippinesHouse of Representatives2019 Mixed-member majoritarian1 (local districts), 61 (nationwide constituency)Parallel voting / superposition (MMM): First-past-the-post (FPTP/SMP) in single-member districts (243 in 2019) + List PR (closed lists; modified Hare quota with 3-seat cap and no remainders) (61 in 2019)304Presidential systemRussian FederationState Duma2021 Mixed-member majoritarianParallel voting / superposition (MMM):