[EM] Condorcet for public proposals - Tounament

[Dave Ketchum]

On Tue, 27 Jan 2004 21:28:52 -0800 Ernest Prabhakar wrote:

> Hi Dave,
> 
> Thanks for the input, very helpful.  More comments below:
> 
> On Jan 27, 2004, at 7:29 PM, Dave Ketchum wrote:
> 
>> I like what Ernest writes, though I see a bit of room for improvement 
>> and suggest "tournament" as a less foreign-sounding title (even though 
>> its ancestry is also French).
> 
> 
> Hmm, maybe.  It is better than Condorcet, but to me tournament evokes an 
> image of knights jousting on horses.
> 
> Someone (sorry, I forgot who) suggested the word Pairwise is important. 
>    I could live with the name Pairwise Matchup Voting (PMV). Pairwise by 
> itself seems too vague, somehow


This thread is looking for something for the public, rather than what we 
might enjoy within our group.

While tournament comes from the time of knights, it gets used for golf 
tours, etc., in the modern world.

I do not demand winning this debate, but think tournament should be 
considered.

> 
>>> Yeah, my friends (on the radical centrist list) are unanimous that 
>>> the term Condorcet has to go. :-)
>>> I have been proposing the term 'Instant Matchup Voting', or IMV, by 
>>> analogy with Instant Runoff Voting. I compare it to a round-robin 
>>> tournament, which most people have direct experience with.  I think 
>>> this leads to a simple, easy to visualize definition:
>>
>>
>> Ahead of much that I have seen, but I suggest tournament as even 
>> easier to visualize from.  My definition will follow yours.
> 
> 
> Well, tournament does have the idea of a series of matches, but not 
> necessarily individual pairwise matchups, I don't think.    We could use 
> the term Instant Round-Robin, which is much more explicit, but IRR is 
> too close to IRV. :-(
> 
>> IMV:
>>
>>> 1. Each rank-ordered ballot is interpreted as a series of "Instant 
>>> Matchups"
>>>     That is A > B > C, implies one point each for the three pairwise 
>>> Matchups A > B, B > C, and A > C
>>>     Note that "A>B" is counted separately from "B>A" (i.e., winning 
>>> votes)
>>> 2. Tally up the N * (N-1) Matchups, for each ordered pair of candidates
>>> 3.  If one candidate beats everyone, that's the absolute winner
>>> 4. If there is a 'rock-paper-scissors' tie (A >= B, B >= C, C >= A),
>>>     the tiebreaking winner is the candidate from that group with the 
>>> 'least greatest defeat'
>>
>> Tournament:
>> 0. Voters simply rank as many of the candidates as they choose, 
>> starting with their most-preferred.
>> 1. Each rank-ordered ballot is interpreted as a series of matches 
>> among all
>> candidates in the election:
>>     That is, ranking A > B > C, and D and E not ranked by this voter,
>> implies each ranked candidate winning over each candidate ranked 
>> later, and
>> over each unranked candidate.
>>
>>      Thus unranked candidates do not get counted as ranked over each 
>> other.
> 
> 
> That's a good point. I don't think we usually spend enough time 
> explaining how the ranking is supposed to work, so it would be good to 
> be more explicit.
> 
>>     Note that "A>B" is counted separately from "B>A" (i.e., winning 
>> votes).
>> 2. Tally up the number of wins for each ordered pair of candidates in an
>> N*N array (with an empty diagonal, for candidates do not play against 
>> themselves).
> 
> 
> Good point, N*N does reduce explanation.
> 

ALSO is easier to program.

>>
>> 3. If one candidate wins when compared with each other candidate, that's
>> the absolute winner.
>> 4. If no absolute winner, we have a 'rock-paper-scissors' near tie such as
>> (A >= B, B >= C, C >= A), and the tiebreaking winner is the candidate from
>> that group with the 'least greatest defeat'.
>>
>> NOTE:  I consider 'least greatest defeat' unacceptably opaque for this 
>> purpose, and ask for help in providing simpler words.
> 
> 
> Fair enough.    How about "whose worst loss is the smallest"?    Or 
> simply "lost by the smallest margin" (a little ambiguous, but sounds 
> simpler) - can always go into more detail elsewhere.
> 

I think I like winning votes rather than margins.

Also hope we can avoid the word "defeat" here.

Do NOT want ambiguity - perhaps someone else can help.

> 
>> BTW:  Debatable whether voters should be permitted to rank candidates 
>> as equal.
> 
> 
> Is there any good reason not to?  Implicit equal ranking certainly makes 
> it clearer about how unlisted candidates are counted.   Any if at all 
> possible, it seems good to give people the option of equality rather 
> than forcing a random choice.    Has anyone presented a clear argument 
> for or against equal ranking?


Complicates the definition a bit.

Complicates ballot construction - without it the ">" is implied.

Perhaps explicit equal ranking simplifies ballot construction:  Let voter 
rank each candidate by number, with equal numbers for equality, and gaps 
in numbers permitted (4,3,1,  ,3 for candidates A thru E ranks C first, B 
and E equal and next, A following, and D unranked).

I deliberately excluded unranked candidates from getting any credit.

> 
>>   If so then, for each pair of equal candidates, count 1/2 win for 
>> each (thus if two voters rank A=B=C then A>B, B>A, A>C, C>A, B>C, and 
>> C>B each get credited one full win).
> 
> 
> That doesn't make any sense to me.   If two candidates are ranked, I 
> think that neither should get the win -- at least if we're doing winning 
> votes (wv) For example, if all the candidates that most people don't 
> rank at the bottom of the list get a win against each other, then one 
> single vote in favor could make that person the 'wv' winner!  Right?
> 

I am following the wv path.  Thus I do not want A and B penalized for some 
voters ranking them equal rather than about half of these voters ranking 
A>B and the other half ranking B>A.

Ok, I am having trouble as to whether the above paragraph matters that 
much for deciding on a winner - certainly does not affect margins in this 
particular race.  Doing these counts does get different numbers in the 
array when A and B are both good candidates and often ranked as equals 
than when they are both unranked lemons.

BTW - the entire array contents BETTER be public - it has much useful 
information beyond the simple deciding on a winner.


> Any more thoughts on the implications of Smith PC on strategy, assuming 
> we can hammer out a decent, simple explanation?
> 
> -- Ernie P.

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  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
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