andrewducker: (Default)
[personal profile] andrewducker
Reminder that any voting system where you can win a single seat without 50% of people thinking you're better than the alternatives is not fit for purpose.

Date: 2025-05-02 11:10 am (UTC)
juan_gandhi: (Default)
From: [personal profile] juan_gandhi
This sounds reasonable, but what's the alternative?

Date: 2025-05-02 02:13 pm (UTC)
simont: A picture of me in 2016 (Default)
From: [personal profile] simont
Strictly speaking, this ends up with 50% of the people who voted thinking that the elected candidate was better than at least one alternative. Not necessarily better than the alternatives, plural.

(Also, 50% of the people who voted, not 50% of the electorate. But surely no voting system can guarantee anything about the latter without making voting mandatory, and I don't think anyone literally does that – even in countries where it's mandatory to show up and do something with a ballot paper, I've not heard of one where spoiling it isn't still an option.)

Date: 2025-05-02 04:32 pm (UTC)
simont: A picture of me in 2016 (Default)
From: [personal profile] simont
Higher than all the other remaining options, after the algorithm started eliminating people, sure. But that's an internal detail of the voting system – if my favourite candidate was eliminated early, I won't consider that I got a candidate I preferred to all the alternatives!

If 1/3 of voters think A > B > C, another 1/3 think B > C > A, and the remaining 1/3 think C > A > B, then, for each of the three candidates, 2/3 of voters would prefer someone else. There's no candidate that 50% or more of voters prefer to the alternatives.

After one candidate is eliminated (say C, because those thirds weren't quite exact), the remaining vote between A and B goes heavily in favour of A, because all the people who had C as first choice preferred A to B. Fine, we have a result, and it's true that 2/3 of people preferred A to B in the notional second-round vote. But that was notional!

The only way you can say that more than half the voters preferred A to the alternatives is if you pretend C wasn't one of the alternatives, because of their elimination in the first round. And since the rounds are instant and happen entirely in the imagination of the algorithm, that hardly seems like a particularly interesting property, especially because you can't use it to compare with other preference-voting systems (like Condorcet-type things) that don't even have internal rounds.

If the winning candidate A pursues a policy that B was dead against, claiming their 2/3 of the vote as a huge mandate of popular support, then maybe they have a point. But if they pursue a policy that C was dead against, on the same grounds, it would clearly be untrue.

Date: 2025-05-02 04:54 pm (UTC)
simont: A picture of me in 2016 (Default)
From: [personal profile] simont
But that's the point, of the options that *could* be elected 50% of the voters preferred one option more than the other.

Which is why I said that you do end up with 50% of the voters preferring the winner to somebody – namely, to whoever survived until the last notional round and then lost it.

It's true that if the elimination process doesn't need to go the full distance then this might look more sensible. And of course I'm not arguing that bloody FPTP is better – when we had the choice to switch to this kind of system I voted in favour. But I don't like to see overstated arguments even for my own position (perhaps especially not for my own position), and I think it's disingenuous to describe it as "50% preferred A to all the alternatives" when what you really mean is "all the alternatives except the ones that my own algorithm decided didn't count".

Date: 2025-05-02 11:12 pm (UTC)
simont: A picture of me in 2016 (Default)
From: [personal profile] simont
Ah, so when you said "preferred to the alternatives", your idea of which alternatives to consider was derived from some first-principles idea other than "the set of candidates eliminated during the IRV process"? That would make more sense, but in that case, was definitely unclear in your original statement of "any voting system that doesn't do this isn't fit for purpose".

Also, I think there are several plausible ways to define the set of not-hopeless candidates. The one that sprang to my mind was the Smith set. But apparently IRV can elect a candidate outside that set, by sometimes eliminating the Condorcet winner if there is one!

Date: 2025-05-03 07:49 am (UTC)
davidcook: (Default)
From: [personal profile] davidcook
Looking at some stats from Australia, where voting is compulsory, (AEC stats on informal voting), the number varies by state and over time, but is typically from 2-10% "informal voting" (which includes people who failed to understand the instructions as well as those who deliberately "spoiled" their ballot or just handed in a blank ballot paper).
Coincidentally, we have a Federal election today, will be interesting to see how our RWNJ parties do ("Trumpet of Patriots", and "Pauline Hanson's One Nation", for example).

Date: 2025-05-02 06:01 pm (UTC)
bens_dad: (Default)
From: [personal profile] bens_dad
Why this focus on ranking preferences ?

To my mind the important point is which candidate is acceptable to the most voters, so why not go with Approval Voting, where each voter says "Yes" or "No" to each candidate*. The candidate with the most "Yes"es wins.

A bit harder to count and recount (and demonstrate that you are doing that fairly), since you cannot sort ballots into a pile for each candidate.

* Make the "No" implied by the absence of "Yes" to avoid blanks.

---

Importantly, neither instant run-off not approval voting work well when you are considering how parties do across a whole elected chamber. Simply consider a chamber where voters in each seat have the same spread of views. Here the same, strongest, party will win every seat, regardless of whether the second party got 0% or 49% of the vote.
Giving each constituency a few seats doesn't help, since the top party will still get all of the seats under both systems.

Our election system is based on people voting for a representative (MP , councillor etc.) and cannot be expected to produce a chamber which accurately reflects the wishes of the electorate as a whole.

I struggled at European elections; our constituencies were so big and had multiple MEPs, so I felt no connection between an MEP and my constituency.

That leaves me thinking that instant run-off versus approval voting versus FPTP missed the important problem, but I have no liking for party lists - that puts real control of who gets a seat into the hands of the parties.

If I thought there was any way it could be implemented, I would ban political parties, but that is not practical, realistic or helpful.

Date: 2025-05-03 09:53 am (UTC)
From: [personal profile] helen_keeble
Under ranking voting systems, the million dollar question becomes how many Conservative voters would rank Labour over Reform.

I am… not optimistic.

(My assumption is that in most constituencies, Greens instantly get eliminated, followed by Lib Dems. Lib Dem and Green votes go to Labour because most of those people are Never Conservative, let alone Reform. Now you’ve either got the situation where Reform are knocked out, in which case it’s a straight up traditional left-vs-right competition between Labour and Conservative, or you have a bunch of Conservative voters playing kingmaker)

Date: 2025-05-03 09:58 am (UTC)
From: [personal profile] helen_keeble
In some ways I feel this weird four party political spectrum situation (again, ignoring Greens) is healthier than the three party situation we’ve had for many years, where the left wing vote was diluted between two parties and the right wing wasn’t.

Though it’s not reassuring that we seem to have ended up with far right, very right, moderately right, and somewhat left as our political options, with everyone but Lib Dems/Greens scrambling to court the Reform voters.

I Disagree

Date: 2025-05-02 05:26 pm (UTC)
bens_dad: (Default)
From: [personal profile] bens_dad
I disagree.

If a candidate is preferred by more than 50% of the voters, but doesn't win, then the voting system is rigged. In that case the voting system is not important.

But we have formal voting systems to cover the common case where no candidate is thought to be the best by 50% of voters.

* A rigged system can be justified in some circumstances.
If the population contains a cohesive minority, such as Catholics in Northern Ireland is could be acceptable to rig it to ensure that the minority gets some seats in government.
But strictly speaking that is more about how the overall chamber is selected than individual seats.

----

[ I have another quibble about your statement -
I have to assume that you meant 50% of the people voting for that seat. ]

Re: I Disagree

Date: 2025-05-02 06:01 pm (UTC)
bens_dad: (Default)
From: [personal profile] bens_dad
But if you have three or more viewpoints with similar levels of support, no candidate can expect to be the first preference for half the voters.

I attempt to address this in my other post.

Date: 2025-05-02 07:51 pm (UTC)
bens_dad: (Default)
From: [personal profile] bens_dad
I read that as implying that unless 50% of people/voters agree on who is the best candidate, an acceptable voting system won't let the seat have a winner.

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