[Election-Methods] SPPA - support building engine

[Stéphane Rouillon]

My advice to Steve is to read all an email before comments.
Cut-off were applied further building the counter-example in the part he 
snipped...
Of course without cut-off, the original ordering method comes back.

"meaningless winners which could not get elected with SPPA in the end."

refers to the fact that the multiple-winner method will not necessarily 
elect a candidate that received the most support
in a district. Again, it is a matter of considering an election as a 
representative exercise and not as a battle.

Stéphane Rouillon

Steve Eppley a écrit :
> Hi,
>
> Stéphane's latest example (immediately below) is very different from his 
> earlier example that I quoted (further below) which he tallied using a 
> voting method he called "Repetitive Condorcet (Ranked Pairs (Winning 
> Votes)) Elimination."  His earlier example had no "approval cutoffs" and 
> his latest example appears to have no connection to Ranked Pairs or 
> Condorcet.  Thus he hasn't provided a basis for claiming my comment was 
> wrong.
>
> My advice to Stéphane for when he sobers up (just joking) is to reread 
> his earlier example and then provide a clear definition of the 
> "Repetitive Condorcet (Ranked Pairs (Winning Votes)) Elimination" 
> method, or a link to its definition, so we will know what voting method 
> he was writing about.  Based on the name he gave it and from his earlier 
> example, it appears (to me, at least) to be the method that iteratively 
> eliminates the candidate ranked last by MAM until one remains.
>
> The thrust of my comment was that since MAM satisfies Peyton Young's 
> LIIA criterion, it follows that MAM elects the same candidate as the 
> more complex voting method that iteratively eliminates the candidate 
> ranked last by MAM until one candidate remains.  Was Stéphane claiming 
> this is wrong, when he wrote that my comment was wrong?
>
> Second, I do not understand what he meant where he wrote, "meaningless 
> winners which could not get elected with SPPA in the end."  I suspect it 
> is not relevant to the comment I made.
>
> --Steve
> ---------------------------------
> Stéphane Rouillon wrote:
>   
>> First Steve's comment is wrong as shown below: A > B > C.
>>     
>>> 33: A > B | C
>>> 31: B > C | A
>>> 33: C | A > B
>>> 3:   B | A > C
>>>
>>> C is eliminated with 33 votes as support.
>>> B is eliminated with 34 votes as support.
>>> A is last eliminated but receives no rallying voters and finishes 
>>> with 33
>>> votes as support.
>>>   B wins.
>>>       
>> Second, as written before, scores or supports matter, not meaningless 
>> winners which could not get elected with SPPA in the end...
>>
>> S.Rouillon
>>
>> Steve Eppley a écrit :
>>     
>>> Hi,
>>>
>>> Assuming I'm correctly understanding a voting method Stéphane 
>>> Rouillon used in a recent message (excerpted below), which he called 
>>> "Repetitive Condorcet (Ranked Pairs(Winning Votes)) elimination," it 
>>> is unnecessarily complicated because it chooses the same winner as 
>>> Ranked Pairs(Winning Votes), which of course is simpler.
>>> Ranked Pairs(Winning Votes), also known as MAM, satisfies H Peyton 
>>> Young's criterion Local Independence of Irrelevant Alternatives 
>>> (LIIA).  One implication of LIIA is that elimination of the 
>>> last-ranked candidate(s) does not change the ranking of the remaining 
>>> candidates.
>>>
>>> By the way, a different criterion has been masquerading as LIIA in 
>>> Wikipedia.  Peyton Young defined the real LIIA in his 1994 book 
>>> Equity In Theory And Practice (if not earlier).
>>>
>>> --Steve
>>> --------------------------------------
>>> Stéphane Rouillon wrote:
>>> -snip-
>>>  
>>>       
>>>> Let's try a counter-example:
>>>>
>>>> 3 candidates A, B, C and 100 voters.
>>>> Ballots:
>>>> 35: A > B > C
>>>> 33: B > C > A
>>>> 32: C > A > B
>>>>
>>>> Repetitive Condorcet (Ranked Pairs(winning votes)  ) elimination 
>>>> would produce
>>>>
>>>> at round 1:
>>>> 68: B > C
>>>> 67: A > B
>>>> Thus ranking A > B > C
>>>> C is eliminated.
>>>>
>>>> at round 2:
>>>> 67: A > B is the ranking
>>>> B is eliminated
>>>>
>>>> at round 3:
>>>> A wins.
>>>>     
>>>>         
>>> -snip-
>>> ----
>>> Election-Methods mailing list - see http://electorama.com/em for list 
>>> info
>>>       
> ----
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>
>   
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