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|Social choice theory|
Plurality-at-large voting (commonly referred to as block/bloc voting or the bloc vote) is a voting system for electing several representatives from a single multimember electoral district using a series of check boxes and tallying votes similar to a plurality election. Although multiple winners are elected simultaneously, block voting is not a system for obtaining proportional representation; instead, the usual result is that the largest single group wins every seat by electing a slate of candidates, resulting in a landslide.
Generally, the term at-large is used to describe elections with multiple winners, however "at-large" sometimes refers to an election for a single candidate running across multiple districts, such as an election for the mayor of a city with multiple city council districts.
Casting and counting ballots
In a block voting election, all candidates run against each other for n number of positions. Each voter selects up to n candidates on the ballot, and the n candidates with the most votes win the positions. Often, voters are said to have "n votes", however they are unable to vote for the same candidate more than once as in cumulative voting. 
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Tactical voting and strategic nomination
Plurality block voting, like single-winner plurality voting, is particularly vulnerable to tactical voting. Supporters of relatively unpopular third parties have a substantial incentive to avoid wasted votes by casting all of their votes for the slate of candidates from a major party.
Parties in block voting systems can also benefit from strategic nomination. Coalitions are actively hurt when they have more candidates than there are seats to fill, as inevitable vote-splitting will occur. Similarly, a coalition has substantial incentive to nominate a full slate of candidates, as otherwise supporting voters may cast some of their remaining votes for opposing candidates.
Bullet voting is a strategy where a voter deliberately only makes a mark for a single candidate in an attempt to not accidentally cause him to be beaten by additional choices. Because the voter is essentially wasting a portion of his vote, bullet voting is only a good strategy when the voter has a strong preference for his favorite and is unsure of (and/or indifferent to) the other candidates' relative chances of winning.
Effects of block voting
The block voting system has a number of features which can make it unrepresentative of the voters' intentions. Block voting regularly produces complete landslide majorities for the group of candidates with the highest level of support. Under block voting, a slate of clones of the top-place candidate is guaranteed to win every available seat. Additionally, like first past the post methods, small cohesive groups of voters can overpower larger numbers of disorganised voters who do not engage in tactical voting, sometimes resulting in a small minority of voters electing an entire slate of candidates by merely constituting a plurality.
While many criticize block voting's tendency to create landslide victories, some cite it as a strength. Since the winners of a block voting election generally represent the same slate or group of voters, there is greater agreement amongst those elected, potentially leading to a reduction in political gridlock.
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Partial block voting
Partial block voting, also called limited voting, functions similarly to plurality-at-large voting, however in partial block voting each voter receives fewer votes than the number of candidates to be elected. This in turn can enable reasonably sized minorities to achieve some representation, as it becomes impossible for a simple plurality to sweep every seat. Partial bloc voting is used for elections to the Gibraltar Parliament, where each voter has 10 votes and 17 seats are open for election; the usual result is that the most popular party wins 10 seats and forms the ruling administration, while the second most popular wins 7 seats and forms the opposition. Partial block voting is also used in the Spanish Senate, where there are 4 seats and each voter receives 3 votes. Historically, partial block voting was used in three- and four-member constituencies in the United Kingdom, where voters received two votes, until multimember constituencies were abolished.
Under partial block voting, the fewer votes each voter is granted the smaller the number of voters needed to win becomes and the more like proportional representation the results can be, provided that voters and candidates use proper strategy.  At the extreme, if each voter receives only one vote, then the voting system becomes equivalent to the Single Non-transferable Vote and the minimum proportion needed is the Droop Quota.
Preferential block voting
Block voting, or plurality block voting is often compared with preferential block voting as both systems tend to produce landslide victories for similar candidates. Instead of a series of checkboxes, preferential block voting uses a preferential ballot. A slate of clones of the top preferred candidate will win every seat under both systems, however in preferential block voting this is instead the instant-runoff winner.
Usage of block voting
Block voting was used in the Australian Senate from 1901 to 1948 (from 1918, this was preferential block voting). It was used for multi-member constituencies in Parliamentary elections in the United Kingdom until their abolition, and remains in use throughout England and Wales for some local elections. It is also used for elections in Jersey and elections in Guernsey.
Plurality block voting is also used in the election of the Senate of Poland, of the Parliament of Lebanon and of the plurality seats in the Palestinian Legislative Council. (In some Lebanese and Palestinian constituencies, there is only one seat to be filled; in the Palestinian election of 1996 there were only plurality seats, while in 2006, half the seats were elected by plurality, half by proportional representation nationwide.) The Senate of the Philippines is elected by plurality in one nationwide district.
A form of plurality block voting was used for the elections of both houses of Parliament in Belgium before proportional representation was implemented in 1900. The system, however, was combined with a system similar to a runoff election; when not enough candidates had the majority of the votes in the first round, a second round was held between the highest ranked candidates of the first round (with two times as many candidates as seats to be filled). In some constituencies there was only one seat to be filled.
Plurality block voting is also in use in the United States today. Although national elections and most state elections use single-member districts, some members of the Maryland House of Delegates and Vermont House of Representatives are elected by block voting from multi-member districts. In local elections such as for city council, however, block voting remains the most popular system in use.
Block voting is often used in corporate elections to elect the boards of directors of corporations including housing cooperatives, with each shareholder's vote being multiplied by the number of shares they own, however cumulative voting is also popular.
- Preferential block voting, a system that produces similar results using a preferential ballot.
- Limited voting, a similar system that produces semi-proportional results where voters are given fewer votes than candidates.
- General ticket, At-Large
- Voting bloc
- Rogers v. Lodge, (1982) Supreme Court Case
- A Handbook of Electoral System Design from International IDEA
- Electoral Design Reference Materials from the ACE Project
- ACE Electoral Knowledge Network Expert site providing encyclopedia on Electoral Systems and Management, country by country data, a library of electoral materials, latest election news, the opportunity to submit questions to a network of electoral experts, and a forum to discuss all of the above