Voting Theory: Instant Runoff Voting

This video explains how to determine the winner of an election using instant runoff voting.
Site: mathispower4u.com

[@JukesMcGee]

Finally, somebody who can gives clear and concise guidelines for this voting method. Good work.

[@dirtworm979]

Thank you for this! I missed my lecture and this caught me up perfectly!

[@therafaels]

There is an error around the 2:50 mark where D should have a total of 19 but the arithmetic incorrectly shows a total of 18. Luckily this does not affect the outcome, but it should be fixed since this video is linked to in a textbook.

[@beavs15]

good video, good explanation, one note tho, at 2:50 in the video it says 9+2+8=18, should 9+2+8=19

[@FluffyKar]

Good thing the votes were not in such a way that would have made D lose with that mistake he made.

[@hilaryb.1955]

Right! I was like wait my calculator can’t be wrong. IRONICALLY this kind of mistake is how votes get corrupted. Yikes!!!

[@mafismathis8012]

2:24 why do you add to D the votes of candidate E? what is the logic behind this?

[@Am-Not-Jarvis]

The 2 voters who made E their first choice vote both made A their second choice, but since A was eliminated, then D was their third choice vote, so their votes go to D as the highest-ranked, still-available choice on their ballot.

[@vincentyan8114]

What if there are 2 or 3 out of 4 candidates having won the same fewest votes in the first counting? In this case which candidate should be eliminated?

[@Anurag_Saxena]

And what if second or third counting? Who will be eliminated first?

[@senseforsale]

The last note about sincerity seems to forget that IRV violates the favorite betrayal criterion. Note that this is the same issue we have with Plurality. IRV merely mitigates this problem in the presence of marginal candidates. But IRV breaks down when those once marginal candidates become more competitive.

[@facudemario3825]

burningice17 what do u mean?

[@vegahimsa3057]

Marginal candidates can be safely ignored by the duopoly in Instant Runoff until "marginal" candidates could have won under plurality.

[@veggiet2009]

I'm looking for the answer of who is eliminated if two candidates tie for last place. None of the authoritative websites seem to have an answer for this. I assumed that both are simultaneously removed, but I realize that eliminating then this way or one at a time could change the outcome, and I've seen a couple references to "multiple methods" for deciding this, but I can't find any source for what those are.

[@vegahimsa3057]

interesting question. Ties are likely rare in a national election. However, among losers, with small counts, perhaps kinda common. In any case IRV is convoluted and doesn't achieve what is claimed. It does not help third parties, does not guarantee sincere voting, and in many cases demands that voters betray favorites.

[@savannahhbrooke]

should have done an example where one was eliminated in the top row first, instead of eliminating the second time around.

[@gabrielpetricec2163]

Can You provide a videó regarding Nanson S method of election éven these method isn't more úsed? Have a Nice day!

[@koreanheart7026]

Consider the preference schedule and determine the winner using the instant runoff voting method(IRV)

[@zlamps]

why does the vote goes to D=9? and not C=8

[@juddmike]

Eliminating E frees up 2 votes. D was "next in line" in that column and gets those. Then eliminating C, who was last of the remaining candidates (8 votes) frees up another 8 - again, D was "next in line" where C was eliminated and received those votes as well. If there was a column where B was next in line after C then s/he would have received those votes, but no-one votes that way.

[@YamadaDesigns]

Condorcet seems really easy to violate.

[@mjohnson6703]

Left one of the E's there.

[@mukeshtiwari]

Sorry, I could not resist. You forgot to delete E in the first column

[@TrendCast314]

i have a quiz in 5 minutes

Score voting is the most fair.

[@vegahimsa3057]

IRV does little to prevent insincere voting. At best it confuses voter strategy. A voter should only vote sincerely when the voter already believes their sincere favorite will either win majority before runoff or be dead last. These outcomes may be predicted with two or three candidates only. But "sincerity only when certain" cannot be considered sincere by any definition. Otherwise, a voter is compelled to always rank a popular frontrunner (lesser evil) first. Some voters second and subsequent ranks will be counted, but a majority of voters second ranks will never be counted. Thus two popular but similar candidates (say Sanders and Warren in 2020 Dem primaries) would both lose under IRV precisely because they were both too popular.

[@libbyreiss3532]

didn't like that I could hear his mouth thanks for the math xoxo