Ranked choice AKA instant runoff voting AKA the arrogantly branded “the alternative vote” is not a good thing.
Changing your ranking for a candidate to a higher one can hurt that candidate. Changing to a lower ranking can help that candidate. IRV fails the monotonicity criterion.
Changing from not voting at all to voting for your favorite candidates can hurt those candidates, causing your least favorite to win. IRV fails the participation criterion.
If candidate A is beating candidate B, adding some candidate C can cause B to win. IRV fails the independence of irrelevant alternatives criterion. In other words, it does not eliminate the spoiler effect.
There are strategic incentives to vote dishonestly.
Due to the way it works, it does not and has not helped third parties.
Votes cannot be processed locally; Auditing is a nightmare.
Et cetera.
If you want a very good and simple single winner election, look to approval voting.
If you’re interested in making that even better in some ways, look to a modification called delegable yes/no voting.
Enacting IRV is a way to fake meaningful voting reform, and build change fatigue, so that folks won’t want to change the system yet again.
How can a change from not voting at all, to voting for favored candidates, hurt those candidates?
2 voters are unsure whether to vote. 13 voters definitely vote, as follows:
6 rank C, A, B
4 rank B, C, A
3 rank A, B, C
If the 2 unsure voters don’t vote, then B wins.
A is eliminated first in this case, for having the fewest top-rank ballots.
The unsure voters both would rank A, B, C.
If they do vote, then B gets eliminated first, and C wins.
By voting, those unsure voters changed the winner from their second choice to their last choice, due to the elimination method which is not as rational as first appears.
How can raising your ranking for a candidate hurt that candidate?
You describe a situation where the public is almost equally divided between the first preference for three candidates. This rarely happens. Be that as it may…
Your donkey vote example I am happy to surrender to as if by a roll of the dice. In the USA, where voting is done electronically, it is easy enough to randomly order candidates for each voter.
The second example, while unfortunate, again is an almost random outcome in a finely balanced field. The two voters still may as well in future put their favorite in the top position despite it randomly turning out to not benefit that candidate.
In such a finely balanced field, the last poster voters see can influence the outcome. The colour of the sunset that day could too.
In electoral systems which use ranked voting, a donkey vote is a cast ballot where the voter ranks the candidates based on the order they appear on the ballot itself. The voter that votes in this manner is referred to as a donkey voter.
But I didn’t intend to provide any donkey vote examples.
Behold, my anti-IRV copypasta:
Ranked choice AKA instant runoff voting AKA the arrogantly branded “the alternative vote” is not a good thing.
Changing your ranking for a candidate to a higher one can hurt that candidate. Changing to a lower ranking can help that candidate. IRV fails the monotonicity criterion.
Changing from not voting at all to voting for your favorite candidates can hurt those candidates, causing your least favorite to win. IRV fails the participation criterion.
If candidate A is beating candidate B, adding some candidate C can cause B to win. IRV fails the independence of irrelevant alternatives criterion. In other words, it does not eliminate the spoiler effect.
There are strategic incentives to vote dishonestly.
Due to the way it works, it does not and has not helped third parties.
Votes cannot be processed locally; Auditing is a nightmare.
Et cetera.
If you want a very good and simple single winner election, look to approval voting.
If you’re interested in making that even better in some ways, look to a modification called delegable yes/no voting.
Enacting IRV is a way to fake meaningful voting reform, and build change fatigue, so that folks won’t want to change the system yet again.
Participation Criterion Failure
Wikipedia offers a simple example of IRV violating the participation criterion, like this:
2 voters are unsure whether to vote. 13 voters definitely vote, as follows:
C,A,BB,C,AA,B,CIf the 2 unsure voters don’t vote, then
Bwins.Ais eliminated first in this case, for having the fewest top-rank ballots.The unsure voters both would rank
A,B,C.If they do vote, then
Bgets eliminated first, andCwins.By voting, those unsure voters changed the winner from their second choice to their last choice, due to the elimination method which is not as rational as first appears.
Monotonicity Criterion Failure
Wikipedia offers a less simple example of IRV violating the monotonicity criterion:
100 voters go to the booths planning to rank as follows:
A,B,CC,B,AB,A,CB,C,AA,C,BC,A,BIf this happens,
Bgets eliminated, andAwins.While in line, 2 folks who planned to rank
C,A,Brealize they actually preferA. They moveAto the top:A,C,B.Now
Cgets eliminated, andBwins.By promoting
Afrom second to first choice, those 2 voters changed the winner fromA, their favorite, toB, their least favorite.You describe a situation where the public is almost equally divided between the first preference for three candidates. This rarely happens. Be that as it may…
Your donkey vote example I am happy to surrender to as if by a roll of the dice. In the USA, where voting is done electronically, it is easy enough to randomly order candidates for each voter.
The second example, while unfortunate, again is an almost random outcome in a finely balanced field. The two voters still may as well in future put their favorite in the top position despite it randomly turning out to not benefit that candidate.
In such a finely balanced field, the last poster voters see can influence the outcome. The colour of the sunset that day could too.
I looked it up on Wikipedia:
But I didn’t intend to provide any donkey vote examples.