Bottom-Two-Runoff IRV: Difference between revisions

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The process: 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.
The process: 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.


The BTR-IRV method was originally proposed by [[User:Legrand|Rob LeGrand]] in 2002, and first referred to by that name by [[Jan Kok]] in 2005.<ref>{{cite web|title=Re: IRV-Condorcet Compromise?|last=LeGrand|first=Rob|website=Instantrunoff-freewheeling Yahoo Group archives|url=https://munsterhjelm.no/km/yahoo_lists_archive/instantrunoff-freewheeling/all_messages/instantrunoff-freewheeling_0465.eml|date=2002-12-20}}</ref><ref>{{cite web|title="Better" IRV?|last=Kok|first=Jan|website=ApprovalVoting Yahoo Group archives|url=https://munsterhjelm.no/km/yahoo_lists_archive/ApprovalVoting/web/2005-July/msg00039.html|date=2005-07-26}}</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 (and in fact, never eliminates all candidates in the [[Smith set]], since a Smith set member can never be eliminated in a runoff against a non-Smith set member). Thus, the method passes the [[Condorcet Criterion]] and the [[Smith criterion]], ensuring it functions as a [[Condorcet method]].
The BTR-IRV method was originally proposed by [[User:Legrand|Rob LeGrand]] in 2002, and first referred to by that name by [[Jan Kok]] in 2005.<ref>{{cite web|title=Re: IRV-Condorcet Compromise?|last=LeGrand|first=Rob|website=Instantrunoff-freewheeling Yahoo Group archives|url=https://munsterhjelm.no/km/yahoo_lists_archive/instantrunoff-freewheeling/web/2002-December/msg00012.html|date=2002-12-20}}</ref><ref>{{cite web|title="Better" IRV?|last=Kok|first=Jan|website=ApprovalVoting Yahoo Group archives|url=https://munsterhjelm.no/km/yahoo_lists_archive/ApprovalVoting/web/2005-July/msg00039.html|date=2005-07-26}}</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 (and in fact, never eliminates all candidates in the [[Smith set]], since a Smith set member can never be eliminated in a runoff against a non-Smith set member). Thus, the method passes the [[Condorcet Criterion]] and the [[Smith criterion]], ensuring it functions as a [[Condorcet method]].


A benefit of BTR-IRV is that first choices are honored in the elimination process, so that a polarizing candidate can survive to later rounds until they have a single opponent who they can be individually compared to. This attribute and ease of explaining the system makes it less prone to claims of fraud than other systems for resolving the [[Condorcet paradox]].
A benefit of BTR-IRV is that first choices are honored in the elimination process, so that a polarizing candidate can survive to later rounds until they have a single opponent who they can be individually compared to. This attribute and ease of explaining the system makes it less prone to claims of fraud than other systems for resolving the [[Condorcet paradox]].
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