[EM] ironclad pro-Condorcet argument?

Steve Eppley seppley at alumni.caltech.edu
Tue Aug 24 12:57:09 PDT 2004

Adam T wrote:
> Steve Eppley wrote:
>> 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. 

To be clear, that's not how I used the term.  I'm 
distinguishing between the Condorcet criterion 
and Condorcet methods.  As I'm using the term--
and others too I think, which is why I'm using it 
this way--Condorcet methods are methods that both: 

   1) use as input the expressions of preference 
      orders submitted by the voters (and ignore
      any additional information from the voters)

   2) satisfy the Condorcet criterion (given 
      sincere votes)

But if people here want to drop #1 from the definition,
I don't mind.

I don't know what Adam meant by "reliably."  Condorcet
winners can lose even if the voting method is Condorcet-
consistent, if some voters strategize and other voters 
don't counter the strategy.  The ease or difficulty of
coordinating counter-strategies depends on the method
and can be used to distinguish between the methods.
(In other words, do they satisfy the non-drastic 
defense criterion?  The minimal defense criterion?  
The sincere defense criterion?)

> Actually, this is a nice, simple way to describe Condorcet 
> methods.  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. 

I expect there'll be disagreement over Adam's use 
of the adjective "accurate."  I agree with him that 
the example method, single-elimination pairings, 
is Condorcet-consistent and a useful analogy.  
(Round-robin pairings is too.)  And I'll return 
to my original point: It's a powerful argument 
for the Condorcet and top cycle criteria that 
single-elimination pairings is the most widely 
used voting method.

To return for a moment to the "Condorcet in 12 words
or less" discussion... How about going through 
a similar exercise for 25 words or less, and an 
exercise to imagine what ought to be shown in 
a short (one minute?) educational video?


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