[EM] Condorcet How?

Dave Ketchum davek at clarityconnect.com
Sat Mar 20 09:08:28 PDT 2010

This is some thought about keeping it simple, yet doable.

I will lean toward Ranked Pairs with margins, but amending toward  
other types of Condorcet should be doable.

Voting:  Voter can rank one or more candidates.  Equal ranking  
permitted.  Counters care only which of any pair of candidates ranks  
higher, not how voter decides on ranking.  Write-ins permitted (if few  
write-ins expected, counters may lump all such as if a single  
candidate - if assumption correct the count verifies it; if incorrect,  
must recount).

Counting:  Besides the N*N matrix, I would add an N array to optimize  
this.  Count each ranked candidate in the array.  Later the array will  
be added into the matrix as if the ranked candidates won in every one  
of their pairs.  This is correct for pairs with no ranking, and for  
pairs with one ranked.  For pairs w/winner and loser, give loser a  
negative count to adjust; for ties can leave both winning; or mark  
both losing via negative count.
      (For example, a ballot with 3 ranks gets 3 counts in N, and  
adjustments for 3 pairs in N*N)

On Mar 10, 2010, at 12:54 AM, Chris Benham wrote:
Re: [EM] Burlington Vermont repeals IRV 52% to 48%
> ...
> I think the name "Ranked Pairs" normally applies to the Margins  
> version.
> http://en.wikipedia.org/wiki/Ranked_Pairs
> "The RP procedure is as follows:
> 	1. Tally the vote count comparing each pair of candidates, and  
> determine the winner of each pair (provided there is not a tie)
> 	2. Sort (rank) each pair, by the largest margin of victory first to  
> smallest last.
> 	3. "Lock in" each pair, starting with the one with the largest  
> number of winning votes, and add one in turn to a graph as long as  
> they do not create a cycle (which would create an ambiguity). The  
> completed graph shows the winner. "
> Chris Benham

More information about the Election-Methods mailing list