[EM] Does IRV elect "majority winners?"

Dave Ketchum davek at clarityconnect.com
Wed Jan 7 20:32:25 PST 2009

On Re: [EM] Does IRV elect "majority winners?" Kristofer Munsterhjelm wrote:
> Dave Ketchum wrote:
>> Condorcet certainly costs more for the system than Plurality.  Costs 
>> bullet-voters nothing - provides a service to whichever voters like to 
>> do more than bullet vote.
>>      Actually can be a service to candidates.  Clinton and Obama had 
>> to try to kill their competitor's campaign for the Democrat nomination 
>> they could not share.  A similar race in Condorcet would let them both 
>> get nominated and have a more civilized fight as to which should be 
>> ranked higher than the other on the ballot.
> If people tend to bullet-vote, it may be the case that elections in 
> general suffer from vote-splitting - simply because if C splits into C1 
> and C2, people either bullet-vote C1 or C2.

In the Condorcet election described above, Clinton and Obama would have 
been ENCOURAGING voters to vote for both of them - that the voters should 
consider both C>O and O>C according to which they preferred.

That is consistent with bullet voting in the many elections where that is 
> On the other hand, the mayor election data that was given on this list 
> earlier seems to show that people don't bullet-vote as much as one would 
> expect (even though one should be careful in deriving conclusions from 
> sample sizes of one).
>> Bucklin deserves more thought as a competitor to Condorcet.
> Bucklin doesn't do that well, Yee-wise. It's simple, however; I'll grant 
> that. As far as criteria go, it fails independence of clones, is not 
> reversal symmetric, and can elect a Condorcet loser (according to WP).
>> How do you count equal ranking in IRV?  If I vote X>A=B>Y, A and B 
>> become visible to the counters at the same time - what does this do to 
>> deciding what candidate is next to mark lost?
> I would assume that if one does A = B > Y and A is eliminated, then the 
> ballot becomes B > Y next - "the ballots are transformed as if the 
> candidate in question never ran".

Note that your words imply that A and B are each counted when neither has 
yet been eliminated - an advantage over the voter having to vote either A>B 
or B>A.

>                                    The difference from A > B > Y or B > A 
>  > Y would be that both would be counted the first time around, either 
> with a full point to each ("whole") or half ("fractional").
>> Approval, Plurality and IRV are distractions from need to pick a live 
>> destination.  I see need to compare, more carefully, Condorcet vs 
>> Range vs Bucklin.
> Range reduces to Approval if enough people use strategy. I think that 
> any version of cardinal ratings should either be DSV or have some sort 
> of Condorcet analysis (like CWP does, or perhaps not that far). Those 
> are my opinions, though, and others (like Abd) may disagree.

Agreed that voters can CHOOSE to express the same restricted thoughts in 
Range as offered by Approval - but Range includes abilities beyond 
Approval's limited ability (just as Condorcet voters can express 
Plurality's limited thought).
>>>> The CW has been compared with EACH other candidate, and found better 
>>>> liked in every case.  However this does not guarantee a majority, 
>>>> since voters are not each required to rank all candidates.
>>> That's right. And, in fact, it could only be a small minority who so 
>>> voted, i.e., that the winner was "better liked." Majority 
>>> requirements *require* that the electorate actually consider and 
>>> accept or reject a winner.
>> A "small minority" cannot win in Condorcet, except for the tortured 
>> case of a zillion candidates with at most a small minority voting for 
>> any one.
>> I am still trying to promote series thought as to need for a majority 
>> for other than Plurality or Approval.
> A worst-case point of view might be to consider the groups maximally 
> different. That is, nobody who voted A > B also voted A > C. From that 
> point of view, and a strict interpretation of "majority", one would have 
> to have the weakest victory be one of a majority - that is, for the 
> candidate X so that the magnitude of the win of A against X is least, A 
> must beat X by a majority.

Let me offer bullet voting in Condorcet:
      32 A
      33 B
      34 C

C wins because, with 99 voters, C's 34 makes it CW.
> This encompasses the standard majority setting where a majority votes A 
>  > [everybody else]. It's not equal to it, as one may see from this example:
> A > B > C > D
> C > B > D > A
> D > B > C > A
> A > B > D > C
> B has a majority against C, D, and A.

Huh?   2 A>B vs 2 B>A?
> It's also a worst-case point of view because it errs "safe" in the case 
> of truncation - truncation so that A is not ranked on the ballot means 
> that no victory for A above some other candidate will be counted for 
> that ballot.

Each ranked candidate counts toward beating each unranked candidate, as 
well as toward beating each lower ranked candidate!
>>>> BTW - cost of ballot support for complete ranking can tempt limits 
>>>> on Condorcet ranking.  How bad should we complain if offered 3 as in 
>>>> RCV?
>> Three seems like a good minimum, with cost vs voter desires 
>> controlling whether more get implemented.
> I don't know much about the cost of optical scanning machines, but 
> presumably getting one with 8 or 10 sensors shouldn't be that more 
> expensive than one with 3. They wouldn't have to be specialized, either, 
> since optical scanning is used for other things than counting ballots.

Eight sensors may be affordable.  How much space on the paper ballot is
required for the eight targets to be sensed - for you do this for each
candidate for each race.
> The ideal solution as far as granularity is concerned would be to have a 
> machine that does OCR, and where voters just write a number in a box 
> next to the candidate (1 for first place, 20 for twentieth). That would 
> be quite a bit more expensive, though, and would also need some sort of 
> fallback... or just manual counting.

Tempting - needs more thought.
  davek at clarityconnect.com    people.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
            Do to no one what you would not want done to you.
                  If you want peace, work for justice.

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