Still seeking to understand the system

Christel

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A neighbour just told me she was told that had she (and others I suppose) given not her first, but her third preference to her most prefered candidate, who wasn't elected, the candidate would have fared better. She doesn't understand why that would be. Is there anything to this?
 


DS-09

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A neighbour just told me she was told that had she (and others I suppose) given not her first, but her third preference to her most prefered candidate, who wasn't elected, the candidate would have fared better. She doesn't understand why that would be. Is there anything to this?
Could you please re-phrase this?
 

stringjack

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A neighbour just told me she was told that had she (and others I suppose) given not her first, but her third preference to her most prefered candidate, who wasn't elected, the candidate would have fared better. She doesn't understand why that would be. Is there anything to this?
If I understand correctly, and assuming we're talking about an Irish election under single transferrable vote, then yes, this can happen. STV fails to satisfy something called monotonicity.
 

wysiwyg

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A neighbour just told me she was told that had she (and others I suppose) given not her first, but her third preference to her most prefered candidate, who wasn't elected, the candidate would have fared better. She doesn't understand why that would be. Is there anything to this?
No.. thats ridiculous

If she gave her first preference to her preferred candidate, thats the best she could do for that candidate

Had she given the candidate her third preference, then that candidate may never have recieved a vote from her... if for example the person she gave the no. 1 to was ahead of her preferred candidate in the count

To be honest Christel, its almost a stupid question
 

ibis

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I think stringjack is correct - because the order in which candidates are eliminated is important. If putting the first two preferences to other candidates would have meant the 'right' candidates were eliminated, things could theoretically have gone better for the preferred candidate. On the other hand, it takes hindsight to see what would have worked...
 

evercloserunion

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That's an odd one alright. I was thinking of one way in which it might happen and I think I had it but lost my train of thought. Could another way be if you vote Candidate A #1, B #2 and C #3, C being your preferred candidate, and A and B transferring heavily to other candidates who are in competition with C for a seat, and your first and second preferences help push A and B over the quote meaning that instead of them being eliminated and all their votes being redistributed, only their surpluses are which would be considerably smaller?

I'm very tired so that probably doesn't work, I dunno.
 

Christel

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If I understand correctly, and assuming we're talking about an Irish election under single transferrable vote, then yes, this can happen. STV fails to satisfy something called monotonicity.
Thanks for your and all other answers so far. And sorry for not having mentioned that I'm still on about the Irish voting system.

Will read your link which seems not easy to understand. My neighbour, who's Irish by the way, wouldn't. This system seems rather distant from common sense, doesn't it?
 

Didimus

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If I understand correctly, and assuming we're talking about an Irish election under single transferrable vote, then yes, this can happen. STV fails to satisfy something called monotonicity.
According to the link you gave "Of the multiple-winner voting systems, all plurality voting methods are monotonic, such as plurality-at-large voting (bloc voting), cumulative voting, and the single non-transferable vote" There is a exception given for a version of stv, but as I understand it it is not the version we use.
So Christel as far as I know, it is not the case that voting someone down the ballot is better than giving them a higher preference. Where you have a favoured second candidate, it can make sense to give them your first preference, if you think your prefered candidate is strong enough not to need your first preference. Can be dangerous though.
Feeling a little fitter now knowing that we have a monotonic voting system -wonder does it do Pilates?
 

ibis

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According to the link you gave "Of the multiple-winner voting systems, all plurality voting methods are monotonic, such as plurality-at-large voting (bloc voting), cumulative voting, and the single non-transferable vote" There is a exception given for a version of stv, but as I understand it it is not the version we use.
So Christel as far as I know, it is not the case that voting someone down the ballot is better than giving them a higher preference. Where you have a favoured second candidate, it can make sense to give them your first preference, if you think your prefered candidate is strong enough not to need your first preference. Can be dangerous though.
Feeling a little fitter now knowing that we have a monotonic voting system -wonder does it do Pilates?
Nope, and I'm afraid it isn't monotonic either.
 

Celtic Raven

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Got it. Lets say you wanted the SDLP to win, and had, in the race for the final seat:

Alliance 1751
UUP 1750
SDLP 1400
Sinn Fein 1001
IRSP 1000

You would be better off voting 1. IRSP 2. UUP 3. SDLP



This type of situation is extremely rare.
 

stringjack

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Thanks for your and all other answers so far. And sorry for not having mentioned that I'm still on about the Irish voting system.

Will read your link which seems not easy to understand. My neighbour, who's Irish by the way, wouldn't. This system seems rather distant from common sense, doesn't it?
You'll need to work through the example given for instant-runoff voting quite carefully, ideally with pen and paper. Instant-runoff voting is STV when there's only one seat, so in Ireland, at national level, that's generally presidential elections and by-elections (moreover, once you're down to the last seat in a multi-seat election, I think the case is functionally equivalent to a single-seat constituency, but I haven't thought very hard about that).

Oh, and one of the earlier pioneers of this stuff was Charles Dodgson, better known as Lewis Carroll, which should give you an indication of just how sensible things are likely to get as you venture further down the rabbit hole.

According to the link you gave "Of the multiple-winner voting systems, all plurality voting methods are monotonic, such as plurality-at-large voting (bloc voting), cumulative voting, and the single non-transferable vote" There is a exception given for a version of stv, but as I understand it it is not the version we use.
As far as I know, that is the version we use - STV which simplifies to IRV in single-seat constituencies (something weird may happen with the transfers, which is slightly different from the standard, but I don't think it affects the monotonicity failure).
 

Delphinian

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No, Christel, it would have made no difference. You are always better to give No. 1 to your preferred candidate. It is a single transferable vote system. Your vote once used up by election or elimination is then transferred to your next available preference. It is only transferable once. If you vote 3 for your preferred candidate, then he would get a transferable vote from either of 1 or 2 that you picked. However it is still only one vote. Which is what you have given them by voting No 1 in the first place. Hope I have made it clear! :)
 

Christel

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No, Christel, it would have made no difference. You are always better to give No. 1 to your preferred candidate. It is a single transferable vote system. Your vote once used up by election or elimination is then transferred to your next available preference. It is only transferable once. If you vote 3 for your preferred candidate, then he would get a transferable vote from either of 1 or 2 that you picked. However it is still only one vote. Which is what you have given them by voting No 1 in the first place. Hope I have made it clear! :)
I was thinking today that probably my neighbour understood something wrong or phrased it not accurately.

It's clear that a candidate needs a certain amount of first preference votes to stay in the race, more than those who are first eliminated. Amount needed of these depends of the number of candidates, available seats and distribution of first preferences?

However, I looked at the relevant back issue of my local paper, and in three of four electoral areas highest amount of votes a candidate got was in a "middle count" (i.e. count 3/4 with 8 candidates and 5 seats, count 5 with 7 seats and 17 candidates, count 2 with 6 candidates and 5 seats) , in three of four cases more than any candidate got as first preferences. In the other case first elected candidate had an exceptional high amount of first preferences, that wasn't reached by any other in later counts. Maybe what she told me has something to do with that.

From looking at these tables another question arose: Are surpluses only transfered if they are above a certain amount? I noticed some kept their votes until the end when surplus was only a few votes.
 

stringjack

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I was thinking today that probably my neighbour understood something wrong or phrased it not accurately.

It's clear that a candidate needs a certain amount of first preference votes to stay in the race, more than those who are first eliminated. Amount needed of these depends of the number of candidates, available seats and distribution of first preferences?

However, I looked at the relevant back issue of my local paper, and in three of four electoral areas highest amount of votes a candidate got was in a "middle count" (i.e. count 3/4 with 8 candidates and 5 seats, count 5 with 7 seats and 17 candidates, count 2 with 6 candidates and 5 seats) , in three of four cases more than any candidate got as first preferences. In the other case first elected candidate had an exceptional high amount of first preferences, that wasn't reached by any other in later counts. Maybe what she told me has something to do with that.

From looking at these tables another question arose: Are surpluses only transfered if they are above a certain amount? I noticed some kept their votes until the end when surplus was only a few votes.
OK. So, let's start at the beginning.
 

ibis

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No, Christel, it would have made no difference. You are always better to give No. 1 to your preferred candidate. It is a single transferable vote system. Your vote once used up by election or elimination is then transferred to your next available preference. It is only transferable once. If you vote 3 for your preferred candidate, then he would get a transferable vote from either of 1 or 2 that you picked. However it is still only one vote. Which is what you have given them by voting No 1 in the first place. Hope I have made it clear! :)
If a vote were only transferable once, there would be no point in filling in anything below the first two preferences. Once your first preference candidate was eliminated, your vote would transfer to your second preference, and your other preferences would never come into play.

The 'single' doesn't refer to the vote only being transferable once, but to the value of the vote.
 

Delphinian

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If a vote were only transferable once, there would be no point in filling in anything below the first two preferences. Once your first preference candidate was eliminated, your vote would transfer to your second preference, and your other preferences would never come into play.

The 'single' doesn't refer to the vote only being transferable once, but to the value of the vote.
It matters because your second, third, or further choices could already be eliminated or elected before your first choice candidate is either eliminated or elected therefore allowing your latter choices to be counted.The vote is still only transferable once.
 

stringjack

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The vote is still only transferable once.
No, it isn't. It is transferrable as many times as there are instances where your preferred candidate is eliminated, or elected, and there are candidates still in contention for whom you have expressed a preference.
 

Delphinian

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From looking at these tables another question arose: Are surpluses only transfered if they are above a certain amount? I noticed some kept their votes until the end when surplus was only a few votes.
A surplus will only be transferred if it is greater than the total difference between the bottom candidates and can save one from being eliminated, can make up the total number of votes to a low candidate so that expenses can be claimed, makes up the difference between a candidates votes and the quota. In some counts surpluses have never been transferred because they would have made no difference to the outcome. This mainly occurs when the surplus is only a small number.
 


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