[Election-Methods] IRV ballot is at least as fair as FPTP ballot

[James Gilmour]

Kathy Dopp  > Sent: 26 December 2007 17:53
> > On Dec 25, 2007 9:58 PM, Stéphane Rouillon 
> >  Yes some voters have second-choice considered but they are all still 
> > treated equally.
> 
> Hardly.  Some voters have both their first AND second choices 
> considered and some voters do not.  IRV not only treats 
> voters' ballots very differently, it ensures that there are 
> numerous ways that a candidate is declared a winner who is 
> supported by fewer voters overall than a candidate who loses 
> in the first round.
> 
> This fact is irrefutable, obvious and simple.  Just try some 
> scenarios out in any spreadsheet.
> 
> IRV would only be fair and treat all voters equally if all 
> first AND second choices of all voters were tabulated, with 
> the second choices being given some weight less than the 
> first - ONLY then would IRV not routinely allow numerous ways 
> to declare a candidate a winner who is supported by fewer 
> voters than the candidate who loses in the first round.

Kathy
Your statements are wrong because you have misinterpreted the preference information recorded on the IRV ballots.  As I have said
before, and in other EM threads, the preferences recorded on an IRV ballot are CONTINGENCY choices.  It would be a great help to all
these discussions if both proponents and opponents of IRV would recognise this historical fact.  Because the IRV preferences are
contingency choices, each voter has only one vote and each voter has exactly the same effect on the result, i.e. deciding the
winner.  IRV is a majoritarian voting system and so majoritarian principles apply throughout.  It is a valid criticism of IRV that
it is a majoritarian system, but that is NOT the argument here.  The argument here is about two single-winner, majoritarian voting
systems, IRV and First-Past-The-Post (FPTP or plurality).

IRV treats all voters' ballots identically  -  the Returning Officer follows to the letter (number!!) the instructions each voter
has recorded on his or her ballot paper.

Your statement that IRV "ensures that there are numerous ways that a candidate is declared a winner who is supported by fewer voters
overall than a candidate who loses in the first round" is based on your misconception about the preference information recorded on
the IRV ballots.  Just consider some simple majoritarian single-winner  elections with 100 voters.

Two candidates: A 55 votes, B 45 votes.    
As this is a majoritarian election, there can be no disagreement that A is the undisputed winner.

Three candidates: A 55 votes, B 30 votes, C 15 votes.     
Again, no disagreement that A is the undisputed winner, because this a majoritarian election (so any Condorcian considerations are
irrelevant, though some who favour a Condorcian view may wish to change the voting system!).

Three candidates:  A 45 votes, B 35 votes, C 20 votes.      
This time there is no undisputed winner.  With a MAJORITARIAN approach, the winner could be A or it could be B.  FPTP would give the
result immediately to A, but everyone can see the defect in that decision (except politicians elected by FPTP who believe it is the
only way they will keep their seats).  So, following the majoritarian approach, it is completely reasonable to say to the supporters
of candidate C, we are going to ignore your first preferences and ask you to vote as though only candidates A and B had stood in
this election, as in first example above.  Then a clear majoritarian result will be obtained that, within the constraints of a
single-winner election and a majoritarian voting system, "best" represents the voters.  Each voter has exercised only one vote and
each voter has made an identical contribution to determining the result.

James Gilmour

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