[Election-Methods] SPPA - support building engine

[Stéphane Rouillon]

As asked for: a link to SPPA paper presented at Chicago in April 2007.
http://convention2.allacademic.com/one/mpsa/mpsa07/index.php?click_key=1&PHPSESSID=a6f3cb6bdfc80d157cec9e6b5ffc0add
IRV is the single winner method used as engine to determine the support 
for each candidate in this case.

Steve Eppley a écrit :
> Hi,
>
> It was not that I didn't read the rest of Stephane's earlier message.  
> It was his lack of clarity: His next example looked like he switched to 
> a different voting method, because his description of the tallying was 
> very different and he did not indicate he was using the same method 
> ("Repetitive Condorcet (Ranked Pairs (Winning Votes)) Elimination.").
>
> At this point, I will assume Stephane does not intend to provide a 
> definition of that voting method nor a link to it, and I don't have time 
> to hunt in older messages to see if it was defined once upon a time. 
>
> Regards,
> Steve
> -------------
> Stéphane Rouillon wrote:
>   
>> 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-
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