[EM] "scored condorcet", etc

Tue Nov 22 19:17:10 PST 2005

On Tue, 22 Nov 2005 20:15:11 -0600 Paul Kislanko wrote:

> "Condorcet lets voters rank the candidates, looks at ALL that the voters 
> say, and compares each pair of candidates.  Doing all the counting is easy 
> enough by computer, but a strain by hand.  When there are near ties they 
> can get called cycles and resolution takes thought."
> 
> Defend the statement that "Condorcet looks at ALL that the voters say". No
> method that begins counting from a pairwise matrix can do that. Furthermore,
> there are numerous "Condorcet" methods because there are numerous ways to
> distinguish between the cycles created when ONLY the pairwise matrix is
> used.

ALL that the voters have said is to offer lists of candidates in 
preference order.

Condorcet DOES LOOK at all of that, though the significance is that IRV, 
looking at the same lists, often pays no attention to ends of the lists.

> 
> There isn't even A "Condorcet method". Choose one, and that you have to
> proves that there are many "Condorcet" ways to process "ALL that the voters
> say", though none really do. 

Agreed that there are variations in how the data is processed.  I say 
little about that - just that the pairs get compared.  What claims to be a 
Condorcet method that does not agree on that much?

> 
> 
>>-----Original Message-----
>>From: election-methods-bounces at electorama.com 
>>[mailto:election-methods-bounces at electorama.com] On Behalf Of 
>>Dave Ketchum
>>Sent: Tuesday, November 22, 2005 7:57 PM
>>To: Rob Brown
>>Cc: election-methods at electorama.com
>>Subject: Re: [EM] "scored condorcet", etc
>>
>>On Tue, 22 Nov 2005 20:34:27 +0000 (UTC) Rob Brown wrote:
>>
>>
>>>Kevin Venzke <stepjak <at> yahoo.fr> writes:
>>>
>>>
>>>>Beatpath(wv) satisfies clone independence, monotonicity,
>>>>plurality, minimal defense, Condorcet Loser, Local IIA,
>>>>always elects from Schwartz, always elects from the CDTT..
>>>>It'll be very hard to meet the same properties if you
>>>>design method from scratch.
>>>>
>>>>
>>>Fair enough.  The biggest problem I have with beatpath is 
>>>
>>that I CAN'T ACTUALLY
>>
>>>ELECT ANYONE WITH IT.  (sorry if that looks like shouting, 
>>>
>>but I can't
>>
>>>emphasize that point enough)
>>>
>>>No one is using beatpath in the real world.  I actually 
>>>
>>*can* elect people with
>>
>>>IRV (since I am lucky enough to live in San Francisco), 
>>>
>>even though most
>>
>>>election methods geeks know it's inferior to condorcet 
>>>
>>methods.  Why is that? 
>>
>>>(and more importantly, why is plurality still so much more 
>>>
>>common than any
>>
>>>ranked system?)
>>>
>>
>>Try an electorate with a popular leader, A, and candidates B, 
>>C, and D 
>>each VERY popular with a fraction, such that a possible vote 
>>with IRV or 
>>Condorcet could be:
>>40 B>A
>>35 C>A
>>25 D>A
>>
>>For Plurality A gets no votes so B wins - or perhaps a rerun 
>>between B and C.
>>
>>For IRV discard D as smallest stack - creating a new smallest 
>>stack for A 
>>- so this gets discarded and B wins.
>>
>>For Condorcet 60 like A better than B; 65 like A better than 
>>C; and 75 
>>like A better than D; so A wins.
>>
>>Plurality is simple, people are used to it, and it is, usually, good 
>>enough - stack up the ballots in a stack per candidate, biggest stack 
>>wins, DONE.
>>
>>Condorcet lets voters rank the candidates, looks at ALL that 
>>the voters 
>>say, and compares each pair of candidates.  Doing all the 
>>counting is easy 
>>enough by computer, but a strain by hand.  When there are 
>>near ties they 
>>can get called cycles and resolution takes thought.
>>
>>IRV uses the same ballots and, usually, chooses the same 
>>winner, though 
>>without looking at all that the voters say.  Back to doable by hand - 
>>stacking ballots per choice ala Priority.  Then removing top 
>>candidate 
>>from smallest stack, moving these to next candidate they vote 
>>for, and 
>>repeating until there is a majority winner.
>>      As in the example, not looking at all that the voters 
>>say can pick a 
>>less-than-best winner.
>>      When Condorcet sees a cycle, it is only luck whether 
>>IRV picks the 
>>same winner (really no complaints proper if picked among those tied - 
>>different variations of Condorcet disagree that much).
>>
>>
>>>I don't question that meeting lots of criteria is good, but 
>>>
>>sometimes I question
>>
>>>whether some of the people on this list tend to see things 
>>>
>>in such black and
>>
>>>white terms that they are really missing some important 
>>>
>>points.  For instance,
>>
>>>with regard to, say, the "clone independence" criterion:  
>>>
>>is it possible that
>>
>>>two methods both technically fail this criterion, but that 
>>>
>>one does a whole lot
>>
>>>better than the other on it?  For instance, plurality 
>>>
>>utterly fails this. 
>>
>>>Minmax....seems to me that it would only affected by clone 
>>>
>>candidates in the
>>
>>>most contrived situations.  I think that saying that 
>>>
>>something "fails", without
>>
>>>saying "how badly it fails", is misleading.
>>>
>>>So if MinMax (or the "MinSum" method I proposed) fails some 
>>>
>>criteria, but "only
>>
>>>by a little bit", while having other desirable properties 
>>>
>>that can make it more
>>
>>>"marketable" (i.e. you can actually explain how it is 
>>>
>>tabulated to regular
>>
>>>people in a way they will understand, and show the results 
>>>
>>in a way they will
>>
>>>understand), I think that could far outweigh its technical 
>>>
>>imperfections.
>>
>>> 
>>>
>>>>I'm not so convinced that it's valuable
>>>>for a method to be tunable. I can't imagine how you could really use
>>>>this to fix a perceived problem.
>>>>
>>>>
>>>Well, let me give an example of tunability that currently 
>>>
>>exists in the real
>>
>>>world: the "two-thirds majority" required to, for instance, 
>>>
>>ammend the US
>>
>>>constition.
>>>
>>>Why two-thirds?  It's not a magic number.  It could have 
>>>
>>been three-fourths (as
>>
>>>it is for final adoption of any constitutional amendment in 
>>>
>>state legistatures),
>>
>>>or three-fifths, or 70 percent, or whatever.  Such a thing 
>>>
>>is inherently
>>
>>>tunable, by simply adjusting a variable, rather than by 
>>>
>>selecting a completely
>>
>>>different system.  Typically the value is not going to be 
>>>
>>adjusted for each
>>
>>>election but it will be selected when framing a new 
>>>
>>constution or by-laws,
>>
>>>allowing the framers to select whatever value they want to 
>>>
>>strike the right
>>
>>>balance (in this case between flexibility and stability).
>>>
>>
>>After ratifying the 18th amendment, it took only 14 years for 
>>Congress to 
>>propose ending it with the 21st - and then a few months to ratify the 
>>21st.  Do not want ratifying to be too easy or we would be 
>>changing every 
>>time the wind blows - nor too hard when a true majority are 
>>agreed.   My 
>>example is a true exception - having the 18th made people think more 
>>seriously on the subject.
>>
>>
>>>Now, with electing a single candidate, things are 
>>>
>>different, but tunabilily
>>
>>>could still be valuable.  Here is an example:
>>>
>>>Say one election method tends to pick a non-controversial, 
>>>
>>middle ground
>>
>>>candidate.  Someone that doesn't offend anyone but isn't 
>>>
>>necessarily loved by
>>
>>>many people either.
>>>
>>>Say another method tends to favor a candidate that is 
>>>
>>strongly favored by many,
>>
>>>disregarding whether that candidate is despised by a few.
>>>
>>>Now, wouldn't it be nice if you could, when writing a new 
>>>
>>constitution or
>>
>>>by-laws, decide the exact balance that is desired, to 
>>>
>>encourage harmony while
>>
>>>also allowing for healthy debate?  Rather than having to 
>>>
>>say "should we use
>>
>>>beatpath or minmax or approval or IRV or plurality?", they 
>>>
>>could say "we'll use
>>
>>>the Tun-o-matic system with the harmony factor set to .7".
>>>
>>
>>Need for tunability varies with election method.
>>
>>With Plurality and multiple candidates, many voters cannot completely 
>>express their wishes - so want a rerun when there is reason 
>>to suspect 
>>this may be a problem.
>>
>>With Plurality and two candidates, a majority may be enough.
>>
>>Can allow a win on less than 50% with Condorcet, for voters 
>>have expressed 
>>their wishes more completely, so 30% might be enough with 25% for 
>>strongest runner-up.
>>
>>IRV claims getting a majority - but this is of the ballots 
>>that made it 
>>thru the last rerun.
>>
>>
>>>-rob

-- 
  davek at clarityconnect.com    people.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
            Do to no one what you would not want done to you.
                  If you want peace, work for justice.