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[Hitokage]

http://www.electionmethods.org/IRVproblems.htm

Instant Runoff Voting (IRV) has been officially endorsed by several organizations and is gaining momentum. Unfortunately, however, confusion reigns regarding its advantages and disadvantages. IRV is very good at preventing minor parties from interfering with the two-party system, but it is arguably no better than our current plurality system at expanding the two-party system and giving other parties a chance to actually win elections. Furthermore, if a third party ever does become strong enough under IRV to seriously threaten the two major parties, they could hurt their own cause and wreak havoc with our entire political system, just as they could under our current plurality system.

IRV can prevent the spoiler effect, in which a minor party splits the vote with a major party and tilts the election toward the other major party, hurting its own cause. IRV therefore seems to allow supporters of minor parties to cast protest votes without "wasting" their votes. This advantage is illusory, however, because it applies only as long as those minor parties are sure to lose. As soon as one of those minor parties threatens to become a major party and actually win, its supporters vote for them at the risk of hurting their own cause, just as in the current plurality system. Under IRV, votes for minor parties are therefore symbolic at best, or dangerous at worst. An example will illustrate why.

BTW, under plurality voting, if your voting preference is Nader, Kerry, Bush, then a vote for Nader is mathematically a vote for Bush if Nader is below both. Sorry, Raoul Duke.

 

[Mike Works]

No kidding.

 

[EviLore]

Interesting. IRV does in fact seem pretty poor, but Condorcet voting appears to be too complex for adoption in the US any time soon.

 

[Archaix]

BTW, under plurality voting, if your voting preference is Nader, Kerry, Bush, then a vote for Nader is mathematically a vote for Bush if Nader is below both. Sorry, Raoul Duke.

Yes, and if you want neither to vote for Kerry nor Bush regardless of whether there are other choices, then it is not mathematically a vote for either candidate.

edit: Also, I keep reading through it and can't figure out how the holy hell it hurts the candidate, cause, and party if a "minor" party beats the "major" parties. What am I missing here? How does that "wreak havoc" upon the political system, exactly?

 

[JoshuaJSlone]

From the linked site:

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. But that's the same situation I'm in now if I vote my true preference for the Libertarian!

So this one voter's preferred candidate(s) didn't win, but the majority of people got a candidate they'd prefer. This seems... a positive to me.

 

[Hitokage]

From the linked site:

So this one voter's preferred candidate(s) didn't win, but the majority of people got a candidate they'd prefer. This seems... a positive to me.

By ranking his most-preferred on top, he helped his least-preferred win. His vote was turned upside down. This is a Bad Thing(tm), and is no better than existing plurality voting.

edit: Also, I keep reading through it and can't figure out how the holy hell it hurts the candidate, cause, and party if a "minor" party beats the "major" parties. What am I missing here? How does that "wreak havoc" upon the political system, exactly?

As a minor party becomes less minor in the polls, their influence becomes opposite of what is desired. Explained further elsewhere on the site:

Monotonicity is perhaps the most fundamental criterion for election methods. Common sense tells us that good election methods should be monotonic. Methods that fail to comply are erratic.

A simple example will prove that IRV is non-monotonic. Consider, for example, the following vote count with three candidates {A,B,C}:

8: A,C
5: B,A
4: C,B

In this example, eight voters ranked the candidates (A,C), five ranked them (B,A), and four ranked them (C,B). Candidate C was ranked first by the fewest voters and is eliminated. Since all the voters who ranked C first also ranked B second, B now has nine top-choice votes and wins.

Suppose, however, that two of the voters who had ranked A first reverse their first two preferences so their votes change from (A,C) to (C,A). Now the vote count is:

6: A,C
5: B,A
4: C,B
2: C,A

Candidate B is now ranked first by the fewest voters and is eliminated. Since the five voters who ranked B first also ranked A second, A now has eleven top-choice votes and wins. Hence, the two voters who demoted A from first to second choice caused A to win. That is, they caused A to win by ranking A lower, without changing the relative ordering of the other candidates. IRV therefore fails monotonicity.

For an even more bizarre example, consider the following vote count with four candidates {A,B,C,D}:

7: A,B,C
6: B,A,C
5: C,B,A
3: D,C,B

Applying the rules of IRV, candidate A wins. But suppose the three voters who voted (D,C,B) now promote A from last choice all the way up to first choice, without changing the relative order of the other candidates. Now B wins instead of A. So by promoting A from last to first choice, those voters caused A to lose instead of win. An election method that allows such nonsensical anomalies is erratic and should be rejected.

 

[JoshuaJSlone]

Looking around the site more, basically their reason for trashing on Instant Runoff Voting is because they think there are better methods of ranked voting, like Condorcet. I'm all ears on that; I just have to give it a proper read.

However, I think this thread title sounds too much like a two-party election. They say IRV has issues... because it doesn't always solve all the problems of the plurality method.

 

[EviLore]

So basically, take 3 candidates, Bush, Kerry, and Nader. IRV in theory, would allow you to escape the "lesser of two evils" dilemma by voting for Nader if you choose, but putting down Kerry as your second choice (since Nader will likely not get enough votes, but your vote for nader won't essentially be a vote for bush like it arguably will be in our current system). In a "normal" instance controlled by the 2 party system, all this is allowing you to do is feel good with a symbolic vote for your third party of choice while still improving the chances of the "lesser evil" that you'd rather have in office if it comes down to the Big Two.

However, what the article is saying is that if, say, Nader becomes big thanks in part to the IRV method, eventually a third party may have enough votes to be a serious contender. So, when this happens, this situation is possible:


hypothetically, left------right

---nader---------------kerry------bush---


Voter A (far left) wants Nader in office. He marks down Nader, Kerry on the IRV ballot.
Voter B (right) wants Bush in office. He marks down Bush, Kerry on the IRV ballot.
Voter C (middle/left) wants Kerry in office. He marks down Kerry, Bush on the IRV ballot.

So, what happens if 5000 people are A, 4000 people are C, and 4500 people are B?

These three candidates are the last 3 standing, but there's no majority. In that case you'd take the smallest group, the Voter C group, and transfer it to the second choice candidate. In that case, nader had more applicable votes until the final round, causing Kerry to be eliminated and Bush to get the win.

So in situations with a strong third party, you end up having to think "strategically" and possibly just putting down your lesser of two evils vote and disregarding the third party, unless you want there to be a chance of your least favored candidate to be elected despite your efforts.

(Edit for fixing screwup)

 

[JoshuaJSlone]

By ranking his most-preferred on top, he helped his least-preferred win. His vote was turned upside down. This is a Bad Thing(tm), and is no better than existing plurality voting.

I'd still argue that it's a Good Thing(tm). It may be a Depressing Thing(tm) for this voter that more than half of the population put the Democratic candidate above the Libertarian or Republican candidates he preferred... but I'm more interested in getting the true will of the people, not in a voting method that lets someone use defensive voting strategies.

 

[Hitokage]

No, they trash it because it fails all their tests for a voting system's merit and is actually worse than plurality voting.

http://www.electionmethods.org/evaluation.htm

 

[Hitokage]

I'd still argue that it's a Good Thing(tm). It may be a Depressing Thing(tm) for this voter that more than half of the population put the Democratic candidate above the Libertarian or Republican candidates he preferred... but I'm more interested in getting the true will of the people, not in a voting method that lets someone use defensive voting strategies.

BECAUSE his vote got turned upside down he MUST use defensive voting strategies if he wants his vote to have any desirable influence.

 

[JoshuaJSlone]

Voter A wants Nader in office. He marks down Nader, Kerry on the IRV ballot.
Voter B wants Bush in office. He marks down Bush, Kerry on the IRV ballot.
Voter C wants Kerry in office. He marks down Kerry, Nader on the IRV ballot.

So, what happens if 5000 people are A, 4000 people are C, and 4500 people are B?

These three candidates are the last 3 standing, but there's no majority. In that case you'd Take the smallest group, the Voter C group, and transfer it to the second choice candidate. In that case, nader had more applicable votes until the final round, causing Kerry to be eliminated and Bush to get the win.

I understand the point the site is making, but either you've made a mistake in your own example or I'm not understanding. In your example, if Kerry was eliminated, those C voters switch to Nader, making it 9000 Nader vs 4500 Bush.

 

[EviLore]

Ok, cleared up my above post so that it actually makes sense.

 

[JoshuaJSlone]

No, they trash it because it fails all their tests for a voting system's merit.

Yeah, I guess you're right. I was taking these two segments from the initial link to basically say "At best, it eliminates the spoiler system. At worst, it can just work like the plurality system." which seems better.

IRV can prevent the spoiler effect, in which a minor party splits the vote with a major party and tilts the election toward the other major party, hurting its own cause.

After a third party is competitive, on the other hand, the effect if IRV is equivalent to a plurality system in which many voters are somehow convinced to forget about strategy and vote sincerely

I appreciate the link, Hitokage. I still think that for our current US political climate instant runoff voting would work well... but in the long run alternate methods like Condorcet definitely seem better.

Voter A (far left) wants Nader in office. He marks down Nader, Kerry on the IRV ballot.
Voter B (right) wants Bush in office. He marks down Bush, Kerry on the IRV ballot.
Voter C (middle/left) wants Kerry in office. He marks down Kerry, Bush on the IRV ballot.

So, what happens if 5000 people are A, 4000 people are C, and 4500 people are B?

So to take your example and look at it the way the Condorcet method they describe works, it would take those same ballots and split it into sub-elections, like...

Nader vs Kerry: Kerry wins
Nader vs Bush: Bush wins
Kerry vs Bush: Kerry wins

Thus Kerry would be the winner, since in one-on-one races he individually beats every opponent. If one person doesn't win all their sub-elections with other people... well, I haven't read it in enough detail to explain how that works out yet.

 

[Hitokage]

Well, if voting reform had to be done NOW, Approval Voting would be an optimal pick. I do agree that the idea behind IRV is good, that of enumerating people's preferences instead of single votes, but it's the implementation that's sorely flawed.