Talk:Instant-runoff voting: Difference between revisions

Regarding IIA, I think IRV can fail less.

Here’s a very strong example of IIA failing in IRV. I got this from somewhere on Wikipedia.

6 C > B > D > A

5 D > A > C > B

5 A > C > B > D

4 B > D > A > C

One-choice elects C. IRV elects C, Borda (4-3-2-1) elects C, Copeland elects C. I would elect A in step 8 or step 9.

Taking D out:

 6 C > B > A

10 A > C > B

 4 B > A > C

One-choice elects A, IRV elects A, Borda (3-2-1) elects A, Copeland elects A. I would elect A in step 5 or step 6.

In looking for the above example, I came across this one from the University of Nebraska where One-choice, Borda and IRV fail.

<nowiki>https://mathbooks.unl.edu/Contemporary/sec-5-5-arrow.html</nowiki>

6  A>B>D>C

5  D>B>C>A

4  C>D>B>A

2  B>C>D>A

IRV elects C. I will elect D in step 8

Taking B out:

6  A>D>C

5  D>C>A

4  C>D>A

2  C>D>A

IRV elects C. I will elect D in step 8.

Food for thought. [[User:RalphInOttawa|RalphInOttawa]] ([[User talk:RalphInOttawa|talk]]) 01:44, 8 December 2023 (UTC)