electowiki

Bottom-Two-Runoff IRV: Difference between revisions

Page Discussion

Bottom-Two-Runoff IRV (view source)

Revision as of 06:51, 17 December 2019

246 bytes added ,  4 years ago
Rewording intro, and preparing for merge of BTR-STV into this article
VisualWikitext
(Edited elimination table in previous edit.)
(Rewording intro, and preparing for merge of BTR-STV into this article)
Line 1:
'''Bottom-Two-Runoff IRV''' ('''BTR-IRV''') is a [[voting system]] that selects a single winner using votes that express ranked preferences. BTR-IRV passes the [[Condorcet Criterion]], and is by definition a [[Condorcet method]].
 
The process is as follows: take the two options with the fewest first preference votes. The pairwise loser out of those two options is eliminated, and the next preferences from those ballots are redistributed. This process repeats until there is only one option remaining, and that remaining option is the winner.▼
BTR-IRV was conceived as a sort of [[Instant-runoff voting]]-Condorcet hybrid, in that the runoff it uses is very similar to IRV, but the runoff doesn't ever eliminate a Condorcet Winner.
 
ItBTR-IRV was originally proposed by [[User:Legrand|Rob LeGrand]] in 2006.<ref name=":0">[https://election-methods.electorama.narkive.com/LKfc52OI/an-example-of-btr-stv#post4 election-methods mailing list: An example of BTR-STV]</ref><ref>[https://www.mail-archive.com/election-methods@electorama.com/msg01311.html <nowiki>[EM] DH3 - error by me - should prefer BTR-IRV to Schulze beatpaths?</nowiki>]</ref> It was conceived as a modification to standard [[Instant-runoff voting|Instant-runoff voting (IRV)]] which ensures the runoff doesn't ever eliminate a Condorcet Winner. Thus, the method passes the [[Condorcet Criterion]], ensuring it functions as a [[Condorcet method]].▼
▲The process is as follows: take the two options with the fewest first preference votes. The pairwise loser out of those two options is eliminated, and the next preferences from those ballots are redistributed. This process repeats until there is only one option remaining, and that remaining option is the winner.
 
This system is a form of [[Single transferable vote|single transferable vote (STV)]], and may be referred to by the more general name '''BTR-STV''', thought the multi-winner variant was not originally recommended by LeGrand.<ref name=":0" />
▲It was originally proposed by [[User:Legrand|Rob LeGrand]].<ref>[https://election-methods.electorama.narkive.com/LKfc52OI/an-example-of-btr-stv#post4 election-methods mailing list: An example of BTR-STV]</ref><ref>[https://www.mail-archive.com/election-methods@electorama.com/msg01311.html <nowiki>[EM] DH3 - error by me - should prefer BTR-IRV to Schulze beatpaths?</nowiki>]</ref>
 
=== An example ===
Retrieved from "https://electowiki.org/wiki/Special:MobileDiff/6732"