[EM] FYI: Tacoma park IRV vote data
Kristofer Munsterhjelm
km-elmet at broadpark.no
Wed Apr 15 08:20:39 PDT 2009
Jonathan Lundell wrote:
>> C wins by 70/93 = 75.3% of the votes. What a landslide!
>>
>> (Schulze and MAM gives A > D > C > B, and IRV gives A > B > C = D.)
>
> That's really a mischaracterization of IRV. IRV (and STV in general)
> does not produce a candidate ordering. It simply finds a winner by
> interpreting the ballots as a list of contingent choices. In particular,
> no ranking is implied by order of elimination.
Alright. The point of the ordering was to show that the elimination
method of "eliminate whoever got the most Plurality votes" is rather
bad, and also that it produces a different result than IRV. Schulze and
MAM agrees that C is the next worst candidate, and IRV (like Schulze and
MAM) elects A as the winner.
Let's call the method of my previous post "Worst Runoff". Worst Runoff,
like all single-elimination methods, passes Condorcet Loser - so there's
no way to get it to elect B.
Whether or not IRV produces an ordering is not really important. What is
important is that you can stretch the "elected by a majority" definition
to apply to any elimination system - at least unless you provide the
caveat of "assuming the voters know what the method does, so that when
they submit ranked ballots, they implicitly consent to the method's
treatment of those ballots". If one uses this qualification, then IRV's
property of "elects what a majority of the voters want" is either
incorrect (because the voters don't "know what the method does" to the
intuitive level required) or is a near-tautology (as any method that
takes a majority of the ballots into account would satisfy this criterion).
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