Proportional representation (PR) refers to any of electoral system under which subgroups of an electorate are reflected proportionately in the elected body. The concept applies mainly to political divisions among voters. The aim of such systems is that all votes cast contribute to the result so that each representative in an assembly is mandated by a roughly equal number of voters, and therefore all votes have equal weight. Under other election systems, a bare plurality or a scant majority are all that are used to elect candidates. PR systems provide balanced representation to different factions, usually defined by parties, reflecting how votes were cast. Where only a choice of parties is allowed, the seats are allocated to parties in proportion to the vote tally or vote share each party receives.
Party-list proportional representation (list-PR) is a system of proportional representation based on preregistered political parties, with each party being allocated a certain number of seats roughly proportional to their share of the vote.
The single transferable vote (STV) or proportional-ranked choice voting (P-RCV) is a multi-winner electoral system in which each voter casts a single vote in the form of a ranked ballot. Voters have the option to rank candidates, and their vote may be transferred according to alternative preferences if their preferred candidate is eliminated or elected with surplus votes, so that their vote is used to elect someone they prefer over others in the running. STV aims to approach proportional representation based on votes cast in the district where it is used, so that each vote is worth about the same as another.
Single non-transferable vote or SNTV is an electoral system used to elect multiple winners. It is a semi-proportional variant of first-past-the-post voting, applied to multi-member districts where each voter casts just one vote. It can also be seen as a variant of limited voting where each elector votes only once.
In the study of electoral systems, the Droop quota is the minimum number of votes a party or candidate needs to receive in a district to guarantee they will win at least one seat.
The Webster method, also called the Sainte-Laguë method, is a highest averages apportionment method for allocating seats in a parliament among federal states, or among parties in a party-list proportional representation system. The Sainte-Laguë method shows a more equal seats-to-votes ratio for different sized parties among apportionment methods.
The highest averages, divisor, or divide-and-round methods are a family of apportionment rules, i.e. algorithms for fair division of seats in a legislature between several groups. More generally, divisor methods are used to round shares of a total to a fraction with a fixed denominator.
The quota or divide-and-rank methods make up a category of apportionment rules, i.e. algorithms for allocating seats in a legislative body among multiple groups. The quota methods begin by calculating an entitlement for each party, by dividing their vote totals by an electoral quota. Then, leftover seats, if any are allocated by rounding up the apportionment for some parties. These rules are typically contrasted with the more popular highest averages methods.
An electoraldistrict, sometimes called a constituency, riding, or ward, is a geographical portion of a political unit, such as a country, state or province, city, or administrative region, created to provide the voters therein with representation in a legislature or other polity. That legislative body, the state's constitution, or a body established for that purpose determines each district's boundaries and whether each will be represented by a single member or multiple members. Generally, only voters (constituents) who reside within the district are permitted to vote in an election held there. The district representative or representatives may be elected by single-winner first-past-the-post system, a multi-winner proportional representative system, or another voting method.
The Imperiali quota or pseudoquota is an unusually-low electoral quota named after Belgian senator Pierre Imperiali. Some election laws used in largest remainder systems mandate it as the portion of votes needed to guarantee a seat.
The single transferable vote (STV) is a proportional representation system and ranked voting rule that elects multiple winners. Under STV, an elector's vote is initially allocated to their first-ranked candidate. Candidates are elected (winners) if their vote tally exceeds the electoral quota. Any surplus votes (those exceeding quota) are transferred from winners to the remaining candidates (hopefuls) according to the surplus ballots' next usable back-up preference.
The Huntington–Hill method, sometimes called method of equal proportions, is a highest averages method for assigning seats in a legislature to political parties or states. Since 1941, this method has been used to apportion the 435 seats in the United States House of Representatives following the completion of each decennial census.
In proportional representation systems, an electoral quota is the number of votes a candidate needs to be guaranteed election. They are used in some systems where a formula other than plurality is used to allocate seats.
Proportionality for solid coalitions (PSC) is a criterion of proportionality for ranked voting systems. It is an adaptation of the quota rule to voting systems in which there are no official party lists, and voters can directly support candidates. The criterion was first proposed by the British philosopher and logician Michael Dummett.
The 2005 Lombard regional election took place on 3–4 April 2005. The 8th term of the Regional Council was chosen. Roberto Formigoni was re-elected for the third time in a row President, defeating Riccardo Sarfatti.
Schulze STV is a proposed multi-winner ranked voting system designed to achieve proportional representation. It was invented by Markus Schulze, who developed the Schulze method for resolving ties using a Condorcet method. Schulze STV is similar to CPO-STV in that it compares possible winning candidate pairs and selects the Condorcet winner. It is named in analogy to the single transferable vote (STV), but only shares its aim of proportional representation, and is otherwise based on unrelated principles.
Semi-proportional representation characterizes multi-winner electoral systems which allow representation of minorities, but are not intended to reflect the strength of the competing political forces in close proportion to the votes they receive. Semi-proportional voting systems are generally used as a compromise between complex and expensive but more-proportional systems and simple winner-take-all systems. Examples of semi-proportional systems include the single non-transferable vote, limited voting, and parallel voting.
An electoral or voting system is a set of rules used to determine the results of an election. Electoral systems are used in politics to elect governments, while non-political elections may take place in business, non-profit organisations and informal organisations. These rules govern all aspects of the voting process: when elections occur, who is allowed to vote, who can stand as a candidate, how ballots are marked and cast, how the ballots are counted, how votes translate into the election outcome, limits on campaign spending, and other factors that can affect the result. Political electoral systems are defined by constitutions and electoral laws, are typically conducted by election commissions, and can use multiple types of elections for different offices.
National remnant is an apportionment scheme used in some party-list proportional representation systems that have multi-member electoral districts. The system uses a Largest remainder method to determine some of the seats in each electoral district. However, after the integer part of the seats in each district is allocated to the parties, the seats left unallocated will then be allocated not in each electoral district in isolation, but in a larger division, such as nationwide or in large separate regions that each encompass multiple electoral districts.
Hare–Clark is a type of single transferable vote electoral system of proportional representation used for elections in Tasmania and the Australian Capital Territory. It was one of the first uses of the Gregory method for transfers of winner's surplus votes.
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