[EM] IRV vs Plurality

[Dave Ketchum]

I see some good thoughts here, but will expand some..

On Jan 11, 2010, at 11:45 AM, robert bristow-johnson wrote:
> On Jan 11, 2010, at 8:54 AM, Kathy Dopp wrote:
>> 2010/1/10 Stéphane Rouillon <stephane.rouillon at sympatico.ca>:
>>> Abd Ul,
>>>
>>> from the data you produce, I agree that for the Burlington  
>>> election, IRV did
>>> produce the same result
>>> FPTP would have produced.
>>
>> No it did not. FPTP would have produced different voting behavior and
>> elected the Condorcet winner because voters were fooled into thinking
>> that IRV allowed them to vote sincerely. A Republican has not won for
>> Mayor in Burlington for over a decade. Most of the people who
>> preferred the Republican first would have voted for the Democrat
>
> highly unlikely, Kathy.  in fact, certainly not the case in  
> Burlington.  it would be the Progs and the Dems both wondering if  
> they should vote for the other (wondering which left-leaning party  
> is more established in Burlington).
>
> the old law required 40% plurality, otherwise it goes to a runoff  
> about a month later.  no one thinks, with the Dem in 3rd place with  
> 1st-choice votes, that the runoff would be between *any* other than  
> the Prog and the GOP.  if turnout for the runoff is good, the Prog  
> would win.  if turnout was poor, who knows?  i've see *two* city  
> council elections go to runoff in Ward 7 and both times, the GOP  
> candidate came from behind (*not* having the plurality on Election  
> Day) and beat the other candidate (one time the Indie, the other  
> time the Dem).  but it was with half the turnout or less.  GOPers  
> seem to be more diligent in getting back to the polls on Runoff Day.
>
>
>> and
>> only a few hundred of those needed to do so for the Democrat to win.
>>
>> Plurality is far better than IRV for many many reasons including:
>>
>> 1. preserves the right to cast a vote that always positively affects
>> the chances of winning of the candidate one votes for
>
> and more often than not, *hurt* the credible candidate that is  
> politically more aligned with the candidate one votes for.
>
> 50,000 voting for Nader elected W in 2000.  that is a matter of fact.

Plurality does that only when you vote for one who has a possibility  
of winning.  Sometimes doing that prevents voting for the one you  
prefer but expect to lose.
>
>
>> 2. allows all voters the right to participate in the final counting
>> round in the case of top two runoff or primary/general elections
>
> but IRV does that in an instantaneous way UNLESS some voter changes  
> their mind about their alternative candidate.  IRV or Condorcet (or  
> any ranked ballot) requires the voter to choose *and* *commit* to  
> not just their favorite, but their fallback candidate on the same  
> Election Day.

With Condorcet the voting is all done on one election day, and all  
that the voters rank are considered in the counting.

While the candidates and voters must do their preparation before that  
one act of voting, that single voting round should be all that is  
needed for the counting and deciding on winner.

Note that primaries may be used, but there is no need for them such as  
is true for plurality - multiple candidates for a party can be voted  
for in a Condorcet general election, with voters ranking such  
candidates if and when they choose.
>
>
>> 3. preserves voters' right to understandably verify the election
>> outcomes because the counting is simple enough for them to do,
>> precinct summable
>
> so does Condorcet.

And Condorcet gives a more accurate view since the ballots more  
completely state voters desires and all that they say gets counted.
>
>> 4. preserves the right for local precinct control of the counts or in
>> the case of election contests that cross county lines, local county
>> control of the counting process
>
> so does Condorcet.    i like precinct summable too, but it isn't the  
> end-all requirement for an honest election.
>
>> 5. is far less costly than the IRV counting process
>
> not in Burlington.  once the infrastructure was set up (the ballot  
> scanning machines didn't have to be changed at all, the difference  
> is that the precinct results (that had a record for how each ballot  
> looked) were transferred to city hall and a computer did the rest.   
> because of FoI laws, this record is available for public scrutiny  
> and has been scrutinized.

Topic seems to be that a second look at a ballot is required in IRV  
after it is determined that the top rank lost.  In Condorcet all the  
looking is done in one pass.

Dave Ketchum
>
>> 6. fails fewer of Arrow's fairness criteria than IRV/STV does
>
> but it (plurality) has the worst failures.  this is what has been  
> well known for decades and why election reformers sought something  
> better.  IRV is sorta better but brought it's own pathologies into  
> it.  Condorcet easily beats FPTP in a context where there are 3 or 4  
> credible candidates.
>
> --
>
> r b-j                  rbj at audioimagination.com
>
> "Imagination is more important than knowledge."