[EM] ironclad pro-Condorcet argument?

Adam Tarr atarr at purdue.edu
Tue Aug 24 11:20:15 PDT 2004

Steve Eppley wrote:

>Dave K wrote:
> > AND, they express dislike for Condorcet by their example voting
> > procedure for preferential voting - the procedure shared by IRV
> > and Condorcet.
>I doubt their omission of Condorcet was an expression of
>dislike for Condorcet.  Remember, that section was written
>long before the computer age that made it practical
>to exhaustively tally all the pairings given voters'
>preference orders.

One does not need a computer to quickly tally Condorcet votes.  You just 
tally up a single pairwise matrix in one go.  Here's a suggested method for 
quickly physically tallying the votes, by hand:

1)  For N options, create a large NxN grid (on paper) and label the 
candidates on the rows and columns.  Black out the main diagonal.

2)  Construct N-1 strips from paper or cardboard, that are big enough to 
fully cover one column of the grid.

3)  For each ballot:
   3a) take the candidate(s) at the highest position on the ballot and put 
one of the cardboard strips on top of the column corresponding to that 
   3b) Make one tally mark in every exposed row entry for that candidate(s).
   3c) scratch that candidate off the ballot and return to 3a) if there are 
any names left on the ballot.
   3d) remove the strips and take the next ballot.

The cardboard strips and the crossing off of names are just visual aids to 
make it easy to avoid messing up.  In the time it takes to read through the 
ballots, you have collected a single pairwise matrix.

> >> Here's a simple example:  Someone proposes a bill and
> >> someone else proposes an amended version of the bill.
> >> In the first round of voting, those two alternatives
> >> would be pitted against each other.  The loser of
> >> that vote would be eliminated.  The winner of that
> >> vote would go on to the next round of voting,
> >> a vote between it and the status quo.
> >
> > This example is not Condorcet - in Condorcet all the
> > versions of the bill would contend in a single election.
>Right, we're defining Condorcet as a family of voting
>procedures that accept preference orders from the voters
>and elect the Condorcet winner, if there is one, given
>those votes.

So... really, this is Condorcet.  "Condorcet" just means a voting method 
that reliably satisfies the Condorcet criterion.  Holding pairwise 
eliminations (in any order) until only one candidate remains does satisfy 
Condorcet's criteria.

Actually, this is a nice, simple way to describe Condorcet methods to 
someone.  Tell them it's like a single-elimination tournament where 
candidates pair off against one another and get eliminated.  That's not an 
accurate description of Ranked Pairs or SSD/Beatpath, but it is an accurate 
description of Condorcet.


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