Mixed electoral system

A mixed electoral system or mixed-member electoral system combines methods of majoritarian and proportional representation (PR).^[1]^[2]^[3] The majoritarian component is usually first-past-the-post voting (FPTP/SMP),^[4] whereas the proportional component is most often based on party-list PR. The results of the combination may be mixed-member proportional (MMP), where the overall results of the elections are proportional,^[2] or mixed-member majoritarian, in which case the overall results are semi-proportional, retaining disproportionalities from the majoritarian component.

Mixed-member systems also often combine local representation^[5] (most often single-member constituencies) with regional or national (multi-member constituencies) representation, having multiple tiers.^[6] This also means voters often elect different types of representatives who might have different types constituencies. Some representatives may be elected by personal elections where voters vote for candidates, and some by list elections where voter vote primarily for electoral lists of parties.

In most mixed systems, every voter can influence both the district-based and PR aspects of an election,^[7] such as under parallel voting; in others, the voter casts just one vote (mixed single vote), which is used to contribute to both a personal (usually district) election and to the filling of seats through list system .^[8] Most mixed systems have all the voters contributing to the election of both groups of members.

Types of mixed systems

Compensatory/non-compensatory seat allocation

A major distinction is often made between mixed compensatory systems and mixed non-compensatory systems.^[8] 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 or largest remainder. 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,^[4] 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^[4] 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.

	Popular vote	FPTP seats	PR seats	Total seats (FPTP + PR)
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.

	Popular vote	FPTP seats	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.

	Popular vote	FPTP seats	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.^[9] 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.^[4]

The two common ways compensation occurs are seat linkage compensation (or top-up) and vote linkage compensation (or vote transfer).^[9] 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.^[10]

Compensatory mixed systems
	single vote systems	dual vote systems
Seat linkage	mixed single vote, top-up versions (MSV) single vote MMP single vote AMS (Bolivia, Lesotho)	mixed-member proportional representation (MMP)
		additional member system (AMS)
		alternative vote plus (AV+)
		Hybrids: e.g. parallel voting+AMS (South Korea)
Vote linkage	positive vote transfer (PVT/MSV) Hungarian PVT/MSV (local elections) Romanian PVT/MSV system (2008-2012)	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 systems
	single vote systems	dual vote systems
No linkage	-	parallel voting
Vote linkage	mixed single vote, superposition Italian variant (Rosatellum)	-
Seat linkage	List seats proportional to FPTP seats Pakistan	-

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.^[7] 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.^[4] Another supermixed system is scorporo, which is a hybrid of parallel voting and the mixed single vote).^[7]


Combination	Type	Attributes	System	Example(s) for use
Independent combination	Fusion	Two formulas are used within each district (or one district for the whole electorate)	Majority bonus (MBS)
	Coexistence (hybrid)	Different districts use different systems in one tier	e.g. FPTP/SMP in single-member districts, list-PR in multi-member districts	Democratic Republic of the Congo, Panama
	Superposition	Different tiers use different systems	Parallel voting (e.g. FPTP/SMP locally, list-PR nationally)	Lithuania, Russia
	Superposition	Different tiers use different systems	Single vote mixed-member majoritarian (e.g. FPTP/SMP locally, list-PR nationally)	Italy, Pakistan
Dependent combination	Correction (compensation)	One formula uses the results of other to compensate	Mixed-member proportional representation (MMP)	Germany, New Zealand
			Additional member system (AMS) - the semi-proportional version of MMP	Scotland, Wales
			Compensatory versions of mixed single vote, like positive vote transfer systems (PVT) or single vote MMP	Lesotho, Bolivia
			Majority jackpot system	Armenia, San Marino
	Conditional	Outcome of one formula determines the other formula	e.g. conditional party block voting: party that receives more than 50%, gets all seats otherwise winner gets 50% of seats and rest is distributed proportionally
Combination of combinations	Supermixed	Superposition + correction	Scorporo / negative vote transfer (NVT), Parallel voting + PVT, Parallel voting + AMS	Hungary, South Korea
		Superposition + Fusion	Majority bonus (MBS)	Greece (formerly)
		Coexistence + conditional	e.g. FPTP/SMP in single-member districts, conditional party block voting in multi-member districts	Cameroon, Chad
		Coexistence + correction	Rural-urban proportional representation (RUP)	Denmark (formerly), Iceland (formerly)
		Fusion + correction	Dual-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.

Additional member systems (AMS)

Like parallel voting, MMP and AMS also have a tier of district representatives typically elected by FPTP, and a tier of regional or at-large representatives elected by PR. Unlike parallel voting, MMP and AMS are mixed compensatory systems, meaning that the PR seats are allocated in a manner that corrects disproportionality caused by the district tier. MMP corrects disproportionalities by adding as many leveling seats as needed, this system is used by Germany and New Zealand.

The type of MMP which does not always yield proportional results, but sometimes only "mixed semi-proportional representation" is called an additional member system. If the fixed number of compensatory seats are enough to compensate the results of the majoritarian FPTP/SMP side of the election, AMS is equivalent to MMP, but if not, AMS does not compensate for remaining overhang seats. In Bolivia and Lesotho, where single vote versions of AMS are used with a relatively large number of compensatory seats, results are usually proportional. AMS models used in parts of the UK (Scotland and Wales), with small regions with a fixed number of seats tend to produce only moderately proportional election outcomes.

Majority bonus and majority jackpot systems

Electoral systems with a majority bonus have been referred to as "unconventional mixed systems".^[11] Employed by Armenia, Greece, and San Marino, as well as Italy from 2006 to 2013,^[12] majority bonuses help the most popular party or alliance win a majority of the seats with a minority of the votes, similar in principle to plurality/majoritarian systems. However, PR is used to distribute seats among the opposition parties, and possibly within the governing alliance.

Scorporo and negative vote transfer (NVT)

Scorporo is a two-tier mixed system similar to MMP in that voters have two votes (one for a local candidate on the lower tier, and one for a party list on the upper tier), except that disproportionality caused by the single-member district tier is partially addressed through a vote transfer mechanism.^[13] Votes that are crucial to the election of district-winning candidates are excluded from the PR seat allocation, for this reason the method used by scorporo is referred to as a negative vote transfer system.^[14] The system was used in Italy from 1993 to 2005, and a modified version is currently used in Hungary.^[15]

Mixed ballot transferable vote (MBTV)

MBTV is a mixed compensatory type of systems similar to MSV, except voters can vote separately for a local candidate and as a transfer vote on the compensatory tier.^[16] It is different from MMP/AMS and AV+ in that there is a vote linkage (instead of seat linkage) between the tiers. The two parts of the dual ballot are tied in a way that only those lists votes get counted, which are on ballots that would be transfer votes in an equivalent positive vote transfer MSV system.

Alternative vote plus (AV+)

AV+ is a mixed compensatory system similar to the additional member system, with the notable difference that the district seats are awarded using the alternative vote. The system was proposed by the Jenkins Commission as a possible alternative to FPTP for elections to the Parliament of the United Kingdom.

Dual member proportional (DMP)

DMP is a mixed compensatory system similar to MMP, except that the plurality and PR seats are paired and dedicated to dual-member (two seat) districts. Proposed as an alternative to FPTP for Canadian elections, DMP appeared as an option on a 2016 plebiscite in Prince Edward Island and a 2018 referendum in British Columbia.

Number of votes

Double vote

Most mixed systems allow voters to cast separate votes for different formulas of the electoral system, including:

Parallel voting
Most AMS/MMP systems
AV+ (the first vote is ranked)
Scorporo

Mixed single vote (MSV)

MSV is a type of mixed systems using only a single vote that serves both as a vote for a local candidate and as a party list vote, split ticket voting is not possible. The system was used in Germany in a mixed proportional system,^[10] and is currently used in Hungary as a semi-proportional system as well as Italy in a non-compensatory system. Other mixed systems using a single vote include majority bonus/jackpot systems and DMP.

Other systems that are usually considered mixed, which use a single vote are:

Majority bonus and jackpot (a single party-list vote)
DMP (a vote for a single candidate or a two-candidate ticket)

The RUP systems formerly used in Denmark and Iceland used a single vote, applicable both for the lower-tier constituencies - FPTP in the rural single-member constituencies, and list PR in the urban multi-member constituencies - and for the upper-tier national leveling seats (and in Denmark, also for the middle-tier regional leveling seats in rural areas). The implementation of RUP proposed in Canada foresees urban multi-member districts that use a single transferable vote, alongside single-member rural districts that are grouped in large multi-member regions; the rural districts and their corresponding regions.

Double simultaneous vote (DSV)

A simultaneous vote is a single vote that used in more than one elections held at once, which means it is not a typically regarded as a mixed system.^{[citation needed]}

List of countries using mixed systems

The table below lists the countries that use a mixed electoral system for the first chamber of the legislature. Countries with coexistence-based hybrid systems have been excluded from the table, as have countries that mix two plurality/majoritarian systems. (See also the complete list of electoral systems by country.)

Country	Body	Latest election (year)	Type of mixed system	Seats per constituency	Mixed system	Component electoral systems	Total seats	Number of votes	Typical results	Notes
Andorra	General Council	2023	Non-compensatory	2 (local districts), 14 (nationwide constituency)	Parallel voting (superposition)	Party block voting (PBV) and party-list PR	28	2	semi-proportional	The parish lists and the national list are independent of one another: the same person cannot appear on both the national list and on a parish list, and voters cast two separate ballots (there is no requirement to vote for the same party for both lists).^[17]
Argentina	Legislature of Córdoba Province	2019	Non-compensatory	1 (local districts), 44 (nationwide constituency)	Parallel voting (superposition)		70	2	semi-proportional
	Legislature of Río Negro Province		Non-compensatory
	Legislature of San Juan Province		Non-compensatory
	Legislature of Santa Cruz Province		Non-compensatory
Armenia			Partially compensatory		Majority jackpot system	Party-list PR + party block voting (PBV)
Bolivia	Chamber of Deputies	2020	Compensatory	1 (local districts), ? (regional constituencies), 7 (indigenous seats elected by the usos y costumbres)	Additional member system (AMS) - MMP without levelling seats	First-past-the-post (FPTP/SMP) + Party-list PR		1 (mixed single vote)	proportional	Ballots use a double simultaneous vote with the presidential election^[18]
Djibouti	National Assembly	2018		3-28			65			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)
Georgia	Parliament	2020	Non-compensatory		Parallel voting (superposition)		150		semi-proportional
Germany	Bundestag (lower house of the federal parliament)	2021	Compensatory	1 (local districts), varies (regional constituencies),	Mixed-member proportional representation (MMP) - with levelling seats	Party-list PR + First-past-the-post (FPTP/SMP)	598 + leveling seats	2	proportional	Referred to as personalized proportional representation,^[19] in 1949 as a result of inter-party bargaining.^[20] Originally used single vote version, switched to two vote version before the 1953 election.
Germany	State parliaments, except Bremen, Hamburg Saarland	varies by state	Compensatory	varies by state	Mixed-member proportional representation (MMP) - with levelling seats	Party-list PR + First-past-the-post (FPTP/SMP)	varies by state	varies by state		Bavaria uniquely uses an open-list system for its party-list seats. Baden-Württemberg uses MMP without lists.
Greece	Hellenic Parliament	2019	Non-compensatory		Majority bonus				semi-proportional
Guinea	National Assembly	2020	Non-compensatory	1 (local districts), 76 (national constituency)	parallel voting (superposition)	Party-list PR (Hare quota) + First-past-the-post (FPTP/SMP)	114		semi-proportional
Hungary	National Assembly (Országgyűlés)	2018	Partially compensatory	1 (local districts), 93 (national constituency)	Supermixed: parallel voting (superposition) and positive vote transfer (correction)	First-past-the-post (FPTP/SMP) + national list-PR	199	2	semi-proportional
Italy	Chamber of Deputies	2022	Non-compensatory	1 (147 single-member districts) 245 (national constituency, seats redistributed into 49 multi-member districts) 8 (Italians abroad constituency)^[21]	Superposition	List PR + First-past-the-post (FPTP/SMP)	400	1 (mixed single vote)	semi-proportional	mixed single vote
Italy	Senate	2022	Non-compensatory	1 (74 single-member districts) varies, cannot be less than 2 (20 regional constituencies, seats redistributed into 26 multi-member districts) 4 (Italians abroad constituency) ^[21]	Superposition	List PR + First-past-the-post (FPTP/SMP)	200	1 (mixed single vote)	semi-proportional	mixed single vote
Japan	House of Representatives		Non-compensatory		Parallel voting (superposition)	First-past-the-post (FPTP/SMP) and List PR	289	2
Japan	House of Councillors		Non-compensatory		Parallel voting (superposition)	SNTV and List PR		2
Republic of Korea (South Korea)	National Assembly	2020	Partially compensatory	1 (local districts), 17 supplementary seats (parallel voting), 30 additional seats (AMS),	Supermixed parallel voting (superposition) and additional member system (correction)	Party-list PR + First-past-the-post (FPTP/SMP)		2	semi-proportional
Kyrgyzstan	Supreme Council	2021	Non-compensatory	1 (local districts), 54 (nationwide constituency)	Parallel voting (superposition)	Party-list PR + First-past-the-post (FPTP/SMP)		2	semi-proportional
Lesotho			Compensatory		Additional member system (AMS)			1 (mixed single vote)	proportional
Lithuania	Seimas		Non-compensatory		Parallel voting (superposition)	TRS and List PR	71		semi-proportional
Mauritania
Mexico	Chamber of Deputies	2021	Partially compensatory	1 (local districts), 40 (multi-member districts)	Supermixed parallel voting (superposition) and additional member system (correction)	First-past-the-post (FPTP/SMP) + Party-list PR (Largest remainder:Hare quota)		2	semi-proportional	Since 1996, a party cannot get more seats overall than 8% above its result nationally (i.e., to win 50% of the legislative seats, a party must win at least 42% of the vote nationwide). There are three exceptions on this rule: first, a party can only lose PR-seats due to this rule (and no plurality-seats); second, a party can never get more than 300 seats overall (even if it has more than 52% of the vote nationally); and third, a party can exceed this 8% rule if it wins the seats in the single-member districts.
Mexico	Chamber of Senators	2018	Non-compensatory	3 (local districts), 32 (multi-member districts)	Superposition	Limited (party) block voting locally (2 seats from each constituency to largest party, 1 to the second largest party) + Party-list PR nationwide		1 (mixed single vote)	semi-proportional
Monaco
Mongolia
Morocco
Nepal
New Zealand	House of Representatives		Compensatory		mixed member proportional (MMP)			2
Pakistan	National Assembly		Non-compensatory		Superposition,seat linkage non compensatory	First-past-the-post (FPTP/SMP) for 272 seats + 70 members appointed by parties proportional with seats already won		1
Philippines	House of Representatives	2019	Non-compensatory		Parallel voting (superposition)
Russian Federation	State Duma	2021	Non-compensatory		Parallel voting (superposition)
San Marino	Grand and General Council	2019	Non-compensatory		Majority bonus				semi-proportional
Senegal	National Assembly	2017	Non-compensatory
Seychelles	National Assembly	2020	Non-compensatory
South Africa	Municipal elections including: Local municipalities Metropolitan municipalities	2021	Compensatory	1	MMP with ca. 50% FPTP and 50% AMS	Varies by municipality 7 - 270				Two ballots - one with FPTP candidates (Ward) and the other with just party names (PR). Compensatory seats are based on the sum of both ballots, effectively allocated using the D'Hondt method.
Sri Lanka
Taiwan(Republic of China)	Legislative Yuan	2020	Non-compensatory		Parallel voting (superposition)
Tajikistan	Assembly of Representatives	2020	Non-compensatory		Parallel voting (superposition)
Tanzania	National Assembly	2020	Non-compensatory		Parallel voting (superposition)
Thailand	House of Representatives	next election, last election (2019) was held under MMP	Non-compensatory		Parallel voting (superposition)			2
United Kingdom	Scotland - Scottish Parliament		Compensatory		Additional member system (AMS)			semi-proportional
	Wales - Senedd (Welsh Parliament)		Compensatory		Additional member system (AMS)		2	semi-proportional
	Local elections in London (Assembly)		Compensatory		Additional member system (AMS)
Venezuela	National Assembly	2020	Non-compensatory	1 (local districts), 400 (nationwide constituency)	Parallel voting (superposition)			2
Zimbabwe	National Assembly	2018	Non-compensatory	1 (local districts), 10 (proportional constituencies)	Superposition			1