[EM] Why I Prefer Condorcet] to IRV

[Dave Ketchum]

On Wed, 19 Nov 2008 16:28:29 -0500 Greg <greg at somervilleirv.org> wrote:

 > I have written up my reasons for preferring IRV over Condorcet
 > methods in an essay, the current draft of which is available here:
 > http://www.gregdennis.com/voting/irv_vs_condorcet.html

 > I welcome any comments you have.
 > Thanks, Greg

Parts of the essay are below, together with my comments,  but first a 
couple notes:
      Bullet voting often is desired by voters when it fully expresses 
their desires - sometimes there are not more than two candidates; sometimes 
they have o desire to express thoughts beyond their favorite.  Wanting to 
do this, they may complain if required effort is more than Plurality would 
demand.
      Plurality is a much used election method and is fine when there are 
voters wanting to express more than the bullet voting thought it permits.
      Range/score requires voters to rate candidates.  I like Condorcet 
better, but concede this is batter than Plurality.
      IRV and Condorcet use ranked ballots.  These let voters rank best 
liked and, behind those, others they consider worth voting for.
      IRV is interested most in first rank but, when that does not 
determine a winner, looks at next rank when a voter's first rank cannot win.
      Condorcet looks at all that the voters say, ranking as in a tournament.

>  Why I Prefer IRV to Condorcet
> by Greg Dennis, last edited 11/19/08

> As I attempt to demonstrate below, IRV not only elects Condorcet winners regularly in practice, but in a competitive electoral environment, IRV may actually elect true Condorcet winners more often than Condorcet itself.

Curious, since a proper method would always elect the most qualified 
candidate, assuming there is one.

>  Furthermore, I argue IRV is more politically feasible, prevents obscure 
candidates from winning, and increases the political and technological 
feasibility of proportional representation and other forms of preferential 
voting, including Condorcet itself.

Conceded that IRV is more used, but not that this is deserved.

If O is truly obscure then few voters will rank O>X and neither method will 
declare O as winner.
> 
> Reason #1: IRV has a track record of electing Condorcet winners
> 
> First and foremost, IRV eliminates the most common type of Condorcet failure --- the "spoiler" scenario --- where the presence of a candidate with little core support causes a Condorcet winner with strong core support to lose.

This makes no sense.  IRV can elect those not well liked if enough of the 
voters liking them rank them first.

Condorcet, looking at all that the voters say, will usually not declare B 
winner if more voters rank A>B than B>A.  Cycles are an exception - A>B>C>A 
has too be resolved where ranking leaves a near tie among the best liked.
> 
> Admittedly, there is another situation similar to the spoiler problem --- the "center squeeze" scenario -- in which IRV may fail to elect the Condorcet winner.

I read this as admitting that IRV, not reading all that the voters say, can 
award a nondeserving winner.

Agreed that this is probably rare, but doubt that its frequency is known 
since IRV does not read all that the voters say.
> 
> Reason #2: IRV is less complicated than Condorcet
> 
Need a closer look, considering that Condorcet offers more service.

IRV can look at how many voters ranked each candidate first and, if A has a 
majority, A wins.  Else need to go back to the ballots which ranked Z, the 
least liked, first and count which candidate was next on those ballots - a 
bit messy if the ballots are in multiple precincts.

Condorcet records all that the voters say in an NxN array.  If from 
multiple precincts, add the arrays together.

Can publish the arrays which show, for every pair of candidates, A&B, how 
many A>B & B>A.

The occasional cycles both represent additional information - members would 
each be a winner vs all outside the cycle, but need extra analysis vs each 
other.
> 
> Reason #3: IRV is less susceptible to intuitive strategies
> 
Agreed that, ASSUMING you know how everyone would vote naturally, your 
friends can modify their votes to change the result.

Big problem is how you tell your friends, without others hearing and 
changing their votes to compensate.

DO NOT see what could protect IRV from such strategies.
> 
> Reason #4: IRV ensures that we know where the winner stands
> 
I do not see how this really differs from #3.
> 
> Reason #5: IRV makes Condorcet feasible
> 
Agreed that doing IRV could make Condorcet more attractive - but, if so, 
why not go directly to Condorcet?
> 
> Reason #6: IRV is the best stepping-stone to proportional representation
> 
Current debate concentrates on single-winners such as mayors and governors.

While proportional representation could be better for legislatures,
not clear why that should affect current debate.
> 
> Reason #7: IRV has political momentum
> 
This seems true - but not more important than looking for and trying to do 
what is best.
-- 
  davek at clarityconnect.com    people.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
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