Voting system

Multiple-winner methods

A vote with multiple winners, such as the election of a legislature, has different practical effects than a single-winner vote. Often, participants in the voting system are more concerned with the overall composition of the legislature than exactly which candidates get elected. For this reason, many multiple-winner systems aim for proportional representation, which means that if a given party (or any other political grouping) gets X% of the vote, it should also get approximately X% of the seats in the legislature. Not all multiple-winner voting systems are proportional.

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Non-proportional and semi-proportional methods

Many multiple-winner voting methods are simple extensions of single-winner methods, without an explicit goal of producing a proportional result. Bloc voting, or plurality-at-large, has each voter vote for N options and selects the top N as the winners. The Single Non-transferable Vote system is similar, but each voter votes for only one option. Single Non-transferable Vote is seen as more proportional than bloc voting, because the results are less thoroughly dominated by the majority opinion. Cumulative voting is a rated multiple-winner voting method where the voter distributes a fixed number of points between the options of his choice, and is considered more proportional than bloc voting for the same reason.

Related Topics:
Bloc voting - Single Non-transferable Vote - Cumulative voting

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Other methods are classified as semi-proportional because they encourage proportional results without guaranteeing them. The quota Borda system extends the Borda count to act somewhat like Single Transferable Vote. Proportional approval voting is a theoretical method that does a similar thing with an Approval ballot.

Related Topics:
Quota Borda system - Single Transferable Vote - Proportional approval voting

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Other semi-proportional methods are the mixed methods, which combine the results of a plurality election and a party-list election (described below). These methods include parallel voting and the Additional Member System.

Related Topics:
Parallel voting - Additional Member System

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Proportional methods

Truly proportional methods make some guarantee of proportionality by making each winning option represent approximately the same number of voters. This number is called a quota. For example, if the quota is 1000 voters, then each elected candidate reflects the opinions of 1000 voters, within a margin of error.

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Party-list proportional representation

Most proportional methods are party-list methods, in which voters vote for parties instead of for individual candidates. For each quota of votes a party receives, one of their candidates wins a seat on the legislature. The methods differ in how the quota is determined, or, equivalently, how the proportions of votes are rounded off to match the number of seats.

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The methods of seat allocation can be grouped overall into highest averages methods and largest remainder methods. Largest remainder methods set a particular quota based on the number of voters, while highest averages methods, such as the Sainte-Laguë method and the d'Hondt method, determine the quota indirectly by dividing the number of votes the parties receive by a sequence of numbers.

Related Topics:
Highest averages method - Largest remainder method - Sainte-Laguë method - D'Hondt method

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Independently of the method used to assign seats, party-list systems can be open-list or closed-list. In an open-list system, voters decide which candidates within a party win the seats. In a closed-list system, the seats are assigned to candidates in a fixed order that the party chooses.

Related Topics:
Open-list - Closed-list

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Single transferable vote proportional representation

Single transferable vote is a proportional representation in which voters rank individual candidates in order of preference. Unlike party-list systems, STV does not depend on the candidates being grouped into political parties. Votes are transferred between candidates in a manner similar to instant runoff voting, but in addition to transferring votes from candidates who are eliminated, votes are also transferred from candidates who already have a quota.

Related Topics:
Single transferable vote - Proportional representation - Instant runoff voting

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