Misplaced Pages

Instant-runoff voting: Difference between revisions

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Browse history interactively← Previous editNext edit →Content deleted Content addedVisualWikitext
Revision as of 15:31, 4 January 2003 editOlivier (talk | contribs)Administrators98,448 editsNo edit summary← Previous edit Revision as of 15:36, 4 January 2003 edit undoEnchanter (talk | contribs)Extended confirmed users5,189 editsm Linking Robert's Rules of OrderNext edit →
Line 1: Line 1:
'''Instant runoff voting''' (known as '''alternative vote''' in many countries) is a ] used for ]s in single-member districts. It is used, among other places, to elect the House of Representatives in ] and the president of the Republic of Ireland. It is rarely used in the ], but in March 2002 it was adopted by voters as the means of electing local candidates in ]. Suggested by Robert's Rules of Order, it is increasingly used in the United States for non-governmental elections, including student elections at ], ], ], the Universities of Illinois and Maryland, Vassar and William and Mary. '''Instant runoff voting''' (known as '''alternative vote''' in many countries) is a ] used for ]s in single-member districts. It is used, among other places, to elect the House of Representatives in ] and the president of the Republic of Ireland. It is rarely used in the ], but in March 2002 it was adopted by voters as the means of electing local candidates in ]. Suggested by ], it is increasingly used in the United States for non-governmental elections, including student elections at ], ], ], the Universities of Illinois and Maryland, Vassar and William and Mary.


This system encourages candidates to balance earning core support through winning first choice support and earning broad support through winning the second and third preferences of other candidates' core supporters. As with any winner-take-all voting system, however, any bloc of more than half the voters can elect a candidate regardless of the opinion of the rest of the voters. This system encourages candidates to balance earning core support through winning first choice support and earning broad support through winning the second and third preferences of other candidates' core supporters. As with any winner-take-all voting system, however, any bloc of more than half the voters can elect a candidate regardless of the opinion of the rest of the voters.

Revision as of 15:36, 4 January 2003

Instant runoff voting (known as alternative vote in many countries) is a voting system used for elections in single-member districts. It is used, among other places, to elect the House of Representatives in Australia and the president of the Republic of Ireland. It is rarely used in the United States, but in March 2002 it was adopted by voters as the means of electing local candidates in San Francisco. Suggested by Robert's Rules of Order, it is increasingly used in the United States for non-governmental elections, including student elections at Harvard, MIT, Stanford, the Universities of Illinois and Maryland, Vassar and William and Mary.

This system encourages candidates to balance earning core support through winning first choice support and earning broad support through winning the second and third preferences of other candidates' core supporters. As with any winner-take-all voting system, however, any bloc of more than half the voters can elect a candidate regardless of the opinion of the rest of the voters.

Voting

Each voter ranks at least one candidate in order of preference. In most Australian elections, voters are required to rank all candidates.

Counting The Votes

First choices are tallied. If no candidate has the support of a majority of voters, the candidate with the least support is eliminated. A second round of counting takes place, with the votes of supporters of the eliminated candidate now counting for their second choice candidate. After a candidate is eliminated, he or she may not receive any more votes.

This process of counting is repeated until one candidate is the most favored choice of more than fifty percent of voters.

An example

Four candidates: Andrea, Brad, Carter, and Delilah.

12 voters rank the candidates:

  1. Andrea
  2. Brad
  3. Carter
  4. Delilah

8 voters rank the candidates:

  1. Carter
  2. Brad
  3. Delilah
  4. Andrea

4 voters rank the candidates:

  1. Delilah
  2. Brad
  3. Carter
  4. Andrea

1 voter ranked the candidates:

  1. Brad
  2. Carter
  3. Andrea
  4. Delilah

As none of the candidates have reached 50%, the lowest-ranked candidate, Brad, is eliminated. The one voter for him now has his or her ballot count for Carter. The vote table now stands:

  • Andrea: 12
  • Carter: 9
  • Delilah: 4

Delilah is eliminated. The four voters who supported her have their ballots count for the next eligible candidate on their ballots, which turns out to be Carter.

The vote table now stands:

  • Carter: 13
  • Andrea: 12

Carter is elected.

Potential for Tactical Voting

Tactical voting is more difficult under IRV than under plurality voting or standard runoff voting. However, it is not impossible. The basic premise of tactical voting in IRV is to ensure that the proper mix of candidates are left standing toward the end.

For example, suppose there are three candidates: Andrea, Brad, and Carter. It is expected (maybe due to polling) that Andrea will receive 40% of the initial vote, Brad 31%, and Carter 29%. It is also expected that all of Carter's support will prefer Brad to Andrea, whereas half of Brad's support prefer Andrea to Carter. This is not an absurd situation if you say that Andrea is left-of-center, Brad centrist, and Carter right-of-center. In order to attain victory in the final round, some of Andrea's supporters may break off and instead vote Carter first, then Andrea. This would lift Carter to victory over Brad in the first round, after which, Brad's votes, evenly split, lift Andrea to victory in the second round. This scenario is identical to one that may occur in standard runoff voting.

See also: Runoff voting, Single transfer voting

External links