[Election-Methods] RELEASE: Instant Runoff Voting

[Dave Ketchum]

HUH!!!  How did we get here, where the topic is IRV???

Plurality with runoff:  If Plurality fails to produce a winner. then 
the leading candidates - usually two - are voted on in a separate 
election.

Exhaustive Ballot:  If Plurality fails to produce a winner, then the 
candidate with the fewest votes is eliminated and a further round of 
voting occurs.  This process is repeated for as many rounds as 
necessary until one candidate has a majority.  NOT GOOD to risk having 
many such rounds in a public election with thousands of voters.

IRV (Instant Runoff Voting):  Can be thought of as a descendant of 
either of the above, with the voter permitted to rank multiple 
candidates on a single ballot and the counters to consider only the 
top ranked in each round.  If Plurality fails to produce a winner, 
then the candidate with the fewest votes is eliminated from all 
ballots, all thus exhausted ballots discarded, and a further round of 
counting occurs.  This process is repeated for as many rounds as 
necessary until one candidate has a majority.

I have not done LNH analysis.

On Sun, 27 Jul 2008 00:06:51 +0100 James Gilmour wrote:
> Kathy Dopp  > Sent: Saturday, June 21, 2008 5:20 AM
> 
>>"Later-No-Harm", however, is incompatible with the basic 
>>principles of majority rule, which requires compromise if 
>>decisions are to be made. That's because the peculiar design 
>>of sequential elimination guarantees -- if a majority is not 
>>required -- that a lower preference cannot harm a higher 
>>preference, because the lower preferences are only considered 
>>if a higher one is eliminated.
> 
> 
> The meaning of the second sentence isn't completely clear to me, but I am fairly sure there is a perverse interpretation of
> "majority" in the first sentence.  An IRV election is an Exhaustive Ballot election contracted into one voting event, instead of
> being spread over several rounds in which the one candidate with fewest votes is eliminated at each round.  It is no surprise that
> the numbers of voters participating varies from round to round  -  usually a progressive (or severe) decline.  The votes in an

IRV election might look like this:
 >
 > Round 1	
 > A   4,000
 > B   3,000
   C>A   400
   C>B 1,400
   C     200
   D>B   100
   D     900
 > Total voting 10,000
 >
 > Round 2
  A   4,000
  B   3,100
  C>A   400
  C>B 1,400
  C     200
  Total voting 9,100
 >
 > Round 3
  A  4,400
  B  4,500
  Total voting 8,900.
 >
B is the majority winner in Round 3, that is to say, the majority 
winner of those voters then voting.

DWK

> Exhaustive Ballot election might look like this:
> 
> Round 1	
> A  4,000
> B  3,000
> C  2,000
> D  1,000
> Total voting 10,000
> 
> Round 2
> A  3,500
> B  2,500
> C  1,500
> Total voting 7,500
> 
> Round 3
> A  3,000
> B  2,000
> Total voting 5,000.
> 
> A is the majority winner in Round 3, that is to say, the majority winner of those voters then voting.   And IRV satisfies that
> criterion  -  and the Exhaustive Ballot is the valid comparison for IRV (because that is the origin of IRV).  The only difference is
> that to ensure the integrity of the count (accounting for all ballot papers at all stages of the count), the ballot papers (votes)
> of those who opt out at the later stages (rounds) are recorded as "non-transferable".
> 
> 
> 
>>But many think that 
>>later-no-harm is undesirable
> 
> 
> "Many" on this list may think that, but it is my experience of more than 45 years as a practical reformer explaining voting systems
> to real electors, that 'later no harm' does matter greatly to ordinary electors.  If they think the voting system will not comply
> with 'later no harm', their immediate reaction is to say "I'm not going to mark a second or any further preference because that will
> hurt my first choice candidate  - the one I most want to see elected."  And of course, if you once depart from 'later no harm' you
> open the way to all sorts of strategic voting that just cannot work in a 'later no harm' IRV (or STV) public election with large
> numbers of voters.
> 
> 
> 
>>But many think that 
>>later-no-harm is undesirable because it interferes with the 
>>process of equitable compromise that is essential to the 
>>social cooperation that voting is supposed to facilitate. If 
>>I am negotiating with my neighbor, and his preferred option 
>>differs from mine, if I reveal that some compromise option is 
>>acceptable to me, before I'm certain that my favorite won't 
>>be chosen, then I may "harm" the chance of my favorite being 
>>chosen. If the method my neighbor and I used to help us make 
>>the decision *requires* later-no-harm, it will interfere with 
>>the negotiation process, make it more difficult to find 
>>mutually acceptable solutions. 
> 
> 
> This is all irrelevant because in a public election there is no negotiation between voter and voter or between voter and candidate.
> I know that there are proposal for voting system that would incorporate "negotiation" of various kinds, but none of those was under
> discussion here.
> 
> James Gilmour
-- 
  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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