[EM] questions about SF's version of IRV

[Dave Ketchum]

On Sat, 01 May 2004 00:15:12 -0700 Bart Ingles wrote:

> 
> sdfgdfg sdfgdfs wrote:
> 
>>Hello, I am wondering what you think of the IRV voting
>>system being implimented in SF, specifically:
>>
>>It seems that voters will be only allowed to rank
>>their top three choices, instead of ranking the whole
>>field? Does this make a difference? If so how would
>>this type of difference effect a race with 5
>>candidates and an incumbent, vs. 20 candidates in a
>>non incumbent race? Is it theoretically possible if
>>the 20 candidates formed 3 "alliances" which only
>>voted for each other, then a 51+ percent majority
>>could not be achieved?
>>

To demand ranking all the candidates has to be UNACCEPTABLE - think of the 
CA recall election and how many candidates they had for governor.  Also 
think of the many voters who are not going to do useful thinking beyond 
bullet voting much as they would do in Plurality.

Actually, as a Condorcet backer, I would welcome IRV being so stupid, but 
I want IRV to propose this right for least static in defining Condorcet rules.

Thus, when IRV promoters talk of "majority" they are NOT thinking of 51+ 
percent - they are using this label for their winner, while not talking of 
percents.

> 
> That was my understanding.  Of course, the definition used for
> "majority" under any form of IRV is pretty weak to begin with-- it
> basically means that the Condorcet loser should be eliminated.  In other
> words, if more than half of voters include in their rankings a vote for
> the eventual winner, then you can say that a majority of voters
> preferred the winner over at least one other candidate.  
> 

Assume 10 voters bullet vote:  4A, 3B, & 3C;  A wins, and I believe they 
claim their winner ALWAYS has a majority.


> So with a ten candidate field, the "majority" winner would be preferred
> head-to-head over at least one other candidate (even though the
> remaining eight candidates may have head-to-head majorities over the IRV
> winner).
> 
> But if you limit the choices to three, then even this limited definition
> only works for four or fewer candidates.
> 

Seems to me IRV does NOT have that much trouble here.

Assume four competitive candidates - SF voters can rank them all (by not 
ranking the least liked).

Assume less than four competitive candidates - besides ranking them all as 
above, SF voters can rank some fringe candidates from a selection of up to 
a zillion.

REMEMBER that, while a few voters may desire to rank long lists, it is 
rare that there will be more than four serious candidates, and neither IRV 
nor Condorcet has trouble with candidates they recognize as fringe.

> 
>>Is anyone aware if the SF system will allow people to
>>only choose one choice, I guess what is called
>>"truncation"?
>>
> 
> I think that's probably the case.  The only areas I have heard of that
> require full ranking are ones that can actually accomodate full
> ranking.  I don't think SF would dare try to force people to use all
> three slots.  The resulting spoiled ballots would look bad.
> 
> 
>>Keep in mind that this would be a very first try for
>>IRV, so even with the possibility open for strategic
>>voting people would very likely not know what to do
>>anyways.
>>
> 
> There's nothing wrong with strategic voting under IRV-- it actually
> helps overcome the method's shortcomings, just as strategic voting does
> under simple plurality voting.  Or most other methods, for that matter.

-- 
  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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