Voting

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http://en.wikipedia.org/wiki/Instant-runoff_voting

Instant-runoff voting (IRV) is a voting system used for single-winner elections in which voters rank candidates in order of preference using one ballot. No further voting rounds are required. If no candidate receives a majority of first choices, the candidate with the fewest number of votes is eliminated, and the votes cast for that candidate are redistributed to the remaining candidates according to the voters' indicated preference. This process is repeated until one candidate has a majority among votes for candidates not eliminated. The term "instant runoff" is used because IRV is said to simulate a series of run-off elections tallied in rounds, as in an exhaustive ballot election.[1]

IRV is also referred to as alternative voting or the Alternative Vote (AV) in the United Kingdom, the preferential ballot in Canada, preferential voting in Australia, and sometimes ranked choice voting in the U.S. It is also referred to as the Hare system or Hare method, after Thomas Hare, an inventor of single transferable vote (STV) because IRV is the same as STV for a single seat election: Even though voters can mark multiple candidates in preference order, the elimination process results in only a single transferable vote cast for the office.

At a national level IRV is used to elect the Australian House of Representatives,[2] the President of Ireland,[3] the national parliament of Papua New Guinea and the Fijian House of Representatives.[4] In the United States, it was used historically in various places but was later rescinded. From 2004, it has been used in four local jurisdictions, including San Francisco, California. As of November 2007, IRV has been approved by voters in other jurisdictions, such as Minneapolis, Minnesota and Pierce County, Washington, and is pending implementation. In the United Kingdom, IRV is used for elections for leaders of the Labour Party and the Liberal Democrats, while the supplementary vote form of IRV is used for all direct elections of mayors in England, including for the Mayor of London.[5]

Robert's Rules of Order Newly Revised notes that preferential voting (IRV is the form shown) is especially useful and fair in an election by mail if it is impractical to take more than one ballot, but it is not a substitute for the normal procedure of repeated balloting until a majority is obtained. In such cases it makes possible a more representative result than under a rule that a plurality shall elect. Preferential balloting can be used only if expressly authorized in the bylaws.[6]

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Tactical voting

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Tactical voting (aka strategic voting) is the behavior of voters intentionally providing misleading information to a voting system in order to maximize the utility of their vote.

For example, a voter who thinks her preferred candidate has no chance of victory might vote for a candidate she dislikes in order to prevent victory by an even more disliked candidate.

Analysis of tactical voting relies heavily on game theory.

The Gibbard-Satterthwaite theorem of the 1970s proved that any minimally useful voting system has some form of tactical voting, but the extent to which it effects the timbre and results of the campaign varies dramatically from system to system.

Contents

1 Conditions for Analysis
2 Outside Influence
3 Examples
4 Sources
 

Conditions for Analysis

The game-theoretic analysis of tactical voting usually relies on two assumptions. First, voters are short-term instrumentally rational. That is, voters are only voting in order to make an impact on one election at a time, and they understand how best to use tactical voting to their advantage. This assumption is generally true in real life, but there are significant cases in which it doesn't. Sometimes voters will vote for a candidate they know will lose in the current election in order to show that they're viable in the next election.

The second assumption is that voters have accurate expectations of how other voters will vote. If the information is non-existent, voters have nothing to base their decisions on but their personal preferences, and hence will vote sincerely. If the information exists, but is distorted, it may lead to voters voting tactically for inaccurate conditions.

Therefore, campaigns try hard to shape the information voters receive about the campaign. Some candidates commission their own public opinion polls. Most craft refined media strategies to shape the way voters see their candidacy. In rolling elections, where some voters have information about previous voters' preferences (e.g. presidential primaries in the United States), candidates put disproportionate resources into competing strongly in the first few stages, because those stages affect the reaction of latter stages.


Outside Influence

In many cases, it is difficult to distinguish between tactical voting by voters, and it's analog before the election. For all the same reasons that voters might decide to vote tactically, campaign donors and activists may decide to tactically support or not support candidates with their money and labor, thus leading to results similar to those caused by tactical choices by the voters. A campaign can be sunk before it ever starts because it fails to convince enough sympathetic people that the campaign is viable, and hence worth backing.


Examples

Tactical voting is quite well known in United Kingdom elections. There are three main parties that are represented in the Parliament: the Labour party, the Conservative party and the Liberal Democrats.

Of these three, Labour and the Liberal Democrats are most similar. Many people who prefer the Liberal Democrats vote for the Labour candidate where Labour is stronger and vice-versa where the Liberal Democrats are stronger, in order to prevent the Conservative candidate from winning.


Sources

Making Votes Count, Gary Cox (1997)
The Proof of the Gibbard-Satterthwaite Theorem Revisited, Lars-Gunnar Svensson (1999)
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This page was last modified 04:45, 15 January 2005. Content is available under GNU Free Documentation License.