[EM] About non-monotonicity and non-responding to previous posts...

[robert bristow-johnson]

being pretty much completely converted to the condorcet faith, i have  
no problem with non-monotonicity that happens to non-condorcet  
winners.  i still do not understand any realistic scenario where non- 
monotonicity affects the condorcet winner.

you guys all probably know that in Burlington Vermont, we have an  
active and substantial third party (the Progs) and IRV for the  
mayoral election.  in 2006 it came in handy and the IRV winner was  
also the Condorcet winner.  but in 2009, the Condorcet winner and IRV  
winner and FPTP winner were three different people.  the IRV winner  
was the Prog, the Condorcet winner was the Dem (as you would expect  
because Condorcet does favor centrism), and the FPTP winner was the  
Republican (and there was another serious independent candidate).   
since we know that if the Condorcet winner makes to the IRV final  
round, then that candidate will also win the IRV in the final round,  
it turns out that those on the right that voted for their favorite  
candidate as their first choice, they actually ended up contributing  
to electing their least favorite candidate.  if they had forsaken  
their fav and given their first choice to their second choice  
(excluding the Independent), they could have changed who the mayor  
is.  but with Condorcet, they wouldn't have needed to make that  
choice.  they could have voted for their candidate (who would lose  
either Condorcet or IRV) and not have that first-pick vote hurt their  
2nd-pick and help their last-pick candidate.  the Repubs started a  
huge fuss and some Dems have joined in, and IRV will again be on the  
ballot next town meeting day (March).  IRV might very well get  
repealed in Burlington in 2010.

i've offered this in the past, but if anyone wants a 6 page quick  
read about my spin of what happened in Burlington, i can send it to  
you.  it's written not for experts but for Burlington residents, many  
who never knew there were alternatives to FPTP besides IRV.  i have  
also locked horns with Rob Ritchie several times.  the last time, i  
was too tired responding again to his non-responses to the points i  
have made.  i agree with the goals of fairvote.org, but i think they  
decided to put all of their chips into the IRV column (as the only  
realistic hope to replace FPTP and/or delayed runoffs) and i think  
committing to a flawed system so early was a mistake of theirs.  but  
IRV is still better than FPTP, just not as good as Condorcet.

--

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."




On Nov 4, 2009, at 10:21 AM, Abd ul-Rahman Lomax wrote:

> The question is quoted below. It's a loaded question. Kathy Dopp is  
> an election security expert, and doesn't necessarily "promote" any  
> voting system, but she'd like the system to be precinct summable,  
> for sure. She is also aware of the other issues caused by non- 
> monotonicity, and the peculiar and nauseating LNH satisfaction (see  
> the original paper in which Later No Harm was defined, what's his  
> name?) of STV,  and I assume she'd be likely to support Approval,  
> Range, Bucklin, or possibly a Condorcet-compliant method, which can  
> be matrix-summed, and it's likely that most elections wouldn't  
> require even that.
>
>>
>> On Oct 31, 2009, at 12:18 PM, robert bristow-johnson wrote:
>>
>>>
>>> On Oct 31, 2009, at 10:29 AM, Kathy Dopp wrote:
>>>
>>>> 5. It always amazes me how irrationally the supporters of IRV/STV
>>>> support a nonmonotonic system that creates more problems than it
>>>> solves when there are clearly better alternatives available that
>>>> actually solve more problems than they create.
>>>
>>> so, Kathy, i am curious as to which of these better alternatives
>>> you promote?


On Nov 4, 2009, at 11:20 PM, Stéphane Rouillon wrote:

> Miss Dopp was promoting FPTP in the past, saying IRV is non-monotonic,
> until I showed that FPTP vote-splitting behaviour is non-monotonic  
> too.
>
>> - more voters prefer B to C
>> - a fraction of those voters will vote for A because they even  
>> prefer A to other candidates
>> - thus C can get elected because of vote-splitting between A and B
>>
>> Even if more voters prefer B to C, the result is that C wins over  
>> B. This is clearly non-monotonic.
>> This is a typical vote-splitting case using FPTP.
>