Talk:Instant-runoff voting

Prior Republican/Libertarian example

There was an example that I decided to replace:

Suppose my true preference is for the Libertarian first and the Republican second. Suppose further that the Libertarians are the strongest "minor" party. At some round of the IRV counting process, all the candidates will be eliminated except the Republican, the Democrat, and the Libertarian. If the Libertarian then has the fewest first-choice votes, he or she will be eliminated and my vote will transfer to the Republican, just as I wanted. But what if the Republican is eliminated before the Libertarian? Unless all the Republican votes transfer to the Libertarian, which is extremely unlikely, the Democrat might then beat the Libertarian. If so, I will have helped the Democrat win by not strategically ranking the Republican first.

However, this thinking is flawed. The problem in this case is that the Republicans are not the major party, but the third party. They come in third, that makes them a third party. And they fail to vote second for their Libertarian second choice, so their second choice does not win. This is how it is supposed to work. When third-party voters don't vote for their second choice, the second choice might not win. The proposed solution is that the major-party voters should vote third-party first.

Try this reasoning when Republicans are the major party. They think that Libertarians will not vote Republican second, and there are enough Libertarians to keep the Republicans from winning. So -- even when they have 45% of the vote and Libertarians have 6%, Republicans might agree to vote Libertarian because they would prefer Libertarians to Democrats. Does that sound in any way plausible? So why would major-party Libertarians vote third-party on the assumption that the third-party voters won't vote second for their candidate? Because they have no self-respect.

I was going to try to keep using the Democratic/Republican/Libertarian example given, and explain it better, but it seemed that the party labels were making it hard to express the idea. I thought Andy Jennings' example that I linked to in the article (referred to in Aaron Hamlin's "The Limits of Ranked Choice Voting" essay from February 2019) was a good explanation of favorite betrayal. -- RobLa (talk) 05:58, 16 December 2019 (UTC)

Does anyone call it IRV any more?

At present, what groups or nations call this voting method "Instant Runoff"? In the US, advocates of this method have seized the generic term Ranked Choice Voting (RCV) as their preferred term. Should IRV still be considered the preferred term? - Frankie1969 (talk) 22:24, 27 September 2021 (UTC)

IRV is still the term which everybody uses. RCV is used by one organization in one country. Also, "Rank Choice" refers to the ballot not the system. Nobody in the voting theory community would use RCV in an academic paper. --Dr. Edmonds (talk) 02:19, 28 September 2021 (UTC)

My point is that AFAICT, none of the English-speaking nations that actually use IRV call it IRV. (update) Australia, NZ, Papua call it Preferential Voting. US & Canada call it RCV. UK calls it Alternative Vote. Ireland & India call it STV. So it can't possibly be correct to say it's "the term which everybody uses". - Frankie1969 (talk) 13:21, 28 September 2021 (UTC)

It appears to be called "instant-runoff voting" on English Wikipedia (see w:Instant-runoff voting). I'm not inclined to go against the consensus over there. -- RobLa (talk) 20:56, 28 September 2021 (UTC)

Fixing the shortcomings of IRV

I would like to fix the shortcomings of IRV. For discussion, I offer an eleven step instant runoff process to do that. Some of the examples on this website are reproduced here to illustrate how an IRV process can do better.

Compromise: regarding the Memphis example.

IRV elects Knoxville, some compromises are suggested to avoid electing Knoxville. Nashville will be elected when the 42 Memphis>Nashville>Chattanooga>Knoxville voters flip their votes to Nashville>Memphis>Chattanooga>Knoxville. Alternatively it is suggested that the 26 Nashville>Chattanooga>Knoxville>Memphis voters flip their votes to Chattanooga>Nashville>Knoxville>Memphis to elect Chattanooga, again avoiding the election of Knoxville.

I have Nashville elected in step 8. No need for anyone to compromise.

IRV can fail to pick a good compromise.

38 A>C>B

38 B>C>A

11 C>A>B

13 C>B>A

IRV elects B. I would elect C in step 8.

IRV fails to count the ballots in a way most favorable to the voters.

26 A>B

25 C>B

49 D

IRV elects D. I see a three way tie, and I will elect one of A, B or D in step 11.

IRV is vulnerable to center-squeeze (“the three candidate” example from center-squeeze).

1031 A>B>C

415 B>A>C

446 B>C>A

1108 C>B>A

IRV elects A. I would elect B in step 8. IRV needs to be less vulnerable to center-squeeze, the center candidate, B in this example, should win.

IRV is vulnerable to favorite betrayal: from the favorite betrayal criterion.

10 A>B>C>D

6 B>A>C>D

5 C>B>A>D

20 D>A>C>B

IRV elects B. I would elect A in step 8. IRV needs to be less vulnerable to favorite betrayal, voters should not need to change their votes.

IRV gives supporters of A an opportunity to win if they betray their favorite.

2 C>A>B>D

8 A>B>C>D

6 B>A>C>D

5 C>B>A>D

20 D>A>C>B

IRV elects A. I would still elect A, this time in step 5. Supporters of A should not have to be this sneaky.

Please consider using an eleven step instant runoff process to make IRV more fair. I have used Google Sheets to create a demonstrator. I'm old and not an expert in anything. But I'm pretty sure it works. I will be very embarrassed if I've made typos in the formulae and the results don't make sense. Point it out and I'll fix it. Here's a link to my spreadsheet:

https://docs.google.com/spreadsheets/d/1D1Aeoy3Y17gcnCyVx6AlGEIYneDidRpqn5a-lClC66I/edit#gid=664199959

--RalphInOttawa (talk) 05:00, 2 December 2023 (UTC)