The Library of Parliament has published a wonderful primer on electoral reform in Canada and around the world that scratches the surface of the various options before Canadians. I’ve decided to cut some snippets from the publication to share here with links to the original document so that you may follow-up on your own.
Plurality or Majority Systems
Description: In plurality or majority electoral systems, the winning candidate is the individual who garners the most votes in an electoral district. Depending on the particular rules of the system, the winner may need to receive a plurality (or more votes than the other candidates) or a majority (over 50% of the votes cast).
First Past the Post (FPTP): Under FPTP, an elector casts a single vote for a candidate to represent the electoral district in which the voter resides. Candidates must gain a plurality of votes to be elected.
Alternative Vote (AV): Also used to elect a single candidate per electoral district, this system is often called preferential voting. On the ballot, voters rank the candidates running in their electoral district in order of their preference. To be elected, a candidate must receive a majority of the eligible votes cast. Should no candidate garner a majority on the first count, the candidate with the fewest first-preference votes (lowest-ranked) is dropped, and the second-preference votes on the ballots where that candidate ranked first are assigned to the respective remaining candidates. This process continues until one candidate receives the necessary majority.
Two-Round: Also known as the run-off system, the two-round system has elections with not one but two election days, generally weeks apart. The system used for the first round of voting is largely similar to FPTP, except to win, a candidate must take a majority of the votes cast and not simply a plurality. Should no candidate garner a majority after the first round of voting, a second election is held with only the top two candidates from the first election results. The candidate with the higher number of votes in the second round is elected.
Block Vote: In essence, this system is FPTP but with multi-member constituencies. In each electoral district, voters may cast as many votes as there are seats. For example, if three seats are available in an electoral district, the three candidates with the most votes will be awarded seats.
Origins: Plurality or majority systems can be traced back to historical British parliamentary practice. FPTP continues to be employed to elect members to the United Kingdom (U.K.) House of Commons, and is also the system used today in most countries that were once part of the British Empire or have historical connections to England.
Advantages and Disadvantages: Plurality or majority systems are easy to use and understand, favour the formation of stable majority governments, maintain a geographic link between constituents and members, and encourage broad-based parties. Critiques of plurality or majority systems include that the seat allocation is disproportionate to the popular vote, and the system exaggerates regionalism and wastes votes. Further critiques of the two-round system are that it is the most expensive electoral system, and voter turnout may decrease between the first and second rounds.
Current Use: Australia – Lower house (AV), Canada (FPTP), France (Two-Round), U.K. (FPTP) and the United States (FPTP).
Proportional Representation Systems
Description: As the name suggests, proportional representation (PR) systems seek to closely match a political party’s vote share with its seat allocation in the legislature. Unlike in most plurality systems, in PR systems, voters elect more than one representative per constituency or geographic area. PR tends to be varied and flexible, and the method for calculating seat distribution can be quite complex, with some systems requiring that a minimum threshold of vote share be earned in order for any seats to be allocated. Citizens generally vote for several candidates, or a party, and the results determine which individual members will sit in the legislature, as well as the overall distribution of seats belonging to each party.
List Proportional Representation (List PR): There are two main forms of List PR: closed-list and open-list. Both forms use a regional or national list of candidates in each constituency drawn up by each party before election day.
In closed-list PR, the party ranks the names on the list, and citizens vote for a party, not a specific candidate. Once all votes have been counted, each party is awarded seats in proportion to its share of the national vote. Individual seats are then allocated to candidates of each party in the order in which they are ranked on the party list.
In open-list PR, voters choose a preferred candidate (or candidates) from the list of the party for which they wish to vote. This means that voters effectively determine the order in which the candidates on the list will be awarded seats.
List PR systems are very flexible and have been adapted by the countries using them.
Single Transferable Vote (STV): Citizens in multi-member electoral districts rank candidates on the ballot. They may rank as few or as many candidates as they wish.
In most variations of this system, winners are declared by first determining the total number of valid votes cast, and then establishing a minimum number of votes that must be garnered based on the number of seats to be filled (the “vote quota”). Candidates who receive the number of first-preference votes needed to reach the quota are elected.
If there are still seats to be filled, a two-step count occurs. In the first step, any votes in excess of the quota for elected candidates are redistributed to the second choices indicated on the ballots of the elected candidates, using a weighted formula (this is called “excess transfer”). Candidates who then reach the quota are elected.
If no candidates reach the quota in this way, a second step takes place in which the candidate with the fewest first-preference votes (lowest-ranked) is dropped, and the second-preference votes on the ballots where that candidate ranked first are assigned to the respective remaining candidates.
Such extra counts continue until enough candidates reach the quota to fill all available seats.
Some variations do not involve excess transfer, but only the elimination of the lowest-ranked candidate and the reassigning of the second preferences on the ballots for that candidate. Nonetheless, the counting process still fits the definition of a single, transferable vote.
Single Non-Transferable Vote (SNTV): In this system, as in FPTP and unlike in block vote, each voter selects one candidate only. However, the system differs from FPTP and resembles block vote in that several members are elected per electoral district. The candidates with the highest vote totals are elected. For example, in a constituency where 20 candidates are vying for five available seats, the five candidates with the most votes will all be elected.
Compared to FPTP or block vote, SNTV can facilitate the representation of minority parties and independents, because the minimum number of votes needed to be elected decreases as the number of seats in the constituency increases, giving parties that normally receive a lower percentage of votes a better chance of electing a candidate.
Origins: Discussion of proportional representation can be traced back to the late 1700s. Its first public use was in 1840 during an election held in Adelaide, Australia.16 Some observers have suggested that the implementation of PR systems, especially throughout Europe, was a response to unrepresentative electoral results, with others suggesting economic transformations and the growth of social democratic parties were driving forces.
Advantages and Disadvantages: PR systems produce results most closely matching the actual proportion of votes garnered by parties, permit greater representation of smaller parties, provide for greater choice, and can encourage power-sharing within a Parliament. Critiques of PR systems include that they can be difficult to understand, they tend to create coalition governments, the geographic link between constituent and member is less prominent, they increase the possibility of electing parties with extreme views, the ballots can be long and complicated, and the counting of results time consuming.
Current Use: Australia – Upper House (STV), Austria (Modified Closed-List PR), Belgium (Modified Closed-List PR), Denmark (Open-List PR), Finland (Open-List PR), Ireland (STV), Netherlands (Modified Closed-List PR), Norway (Modified Closed-List PR), Russia (Closed-List PR), South Africa (Closed-List PR), Sweden (Modified Closed-List PR) and Switzerland (Open-List PR).
The modified closed-list PR systems listed above essentially give electors some ability to influence which candidates on party lists are elected by stating preferences on the ballot. The countries use different methods and set different thresholds of vote share needed for election.
Mixed Electoral Systems
Description: Mixed electoral systems combine elements of a plurality or majority system with proportional representation. Citizens in a constituency cast two votes: one to directly elect an individual member to serve as their representative, and a second for a party or parties to fill seats in the legislature allocated according to the proportion of the vote share they receive.
Mixed Member Majority (MMM): Citizens in single-member electoral districts cast two votes: one for a candidate to represent their constituency according to the FPTP system, and one for a party. Each party presents a previously established list of candidates, similar to the List PR system. A predetermined portion of the legislature’s seats are filled using the plurality vote, while the remaining seats are filled by the party list vote.
The two votes under MMM are fully independent of one another; the party seats will not compensate for any disproportionate result in the constituency elections.
Mixed Member Proportional (MMP): This system operates in the same way as MMM, except that a citizen’s second vote, which allocates seats to parties according to List PR, is used to attempt to compensate for any disproportionate results in the FPTP constituency part of the election.
Additional seats are awarded to qualifying parties18 where the number of constituency seats that they won fails to reflect voter support shown in both components of the election.
There are variations among the various MMP systems in how this allocation is made.
Origins: Mixed electoral systems can be traced back to Germany’s adoption of an MMP system following the Second World War. Observers have noted that the system represents a compromise, or third way, between plurality or majority systems, and proportional representation.
Advantages and Disadvantages: Mixed electoral systems provide for fairly proportional outcomes, maintain the geographic link between constituents and members, provide for greater choice, and allow the opportunity for smaller parties to be represented in Parliament. Critiques of mixed electoral systems include that they may be difficult to use and understand, and they create two classes of members (electoral district versus list).
Current Use: Germany (MMP), Japan (MMM), Mexico (MMP), New Zealand (MMP), Philippines (MMM), Scotland (MMP), South Korea (MMM) and Wales (MMP).