[EM] Two simple alternative voting methods that are fairer than IRV/STV and lack most IRV/STV flaws

[Dave Ketchum]

In response I will pick on LNH for not being a serious reason for  
rejecting Condorcet - that such failure can occur with reasonable  
voting choices for which the voter knows what is happening.  Quoting  
from Wikipedia:

> For example in an election conducted using theCondorcet compliant  
> method Ranked pairs the following votes are cast:
> 49: A
> 25: B
> 26: C>B
> B is preferred to A by 51 votes to 49 votes. A is preferred to C by  
> 49 votes to 26 votes. C is preferred to B by 26 votes to 25 votes.
> There is no Condorcet winner and B is the Ranked pairs winner.
> Suppose the 25 B voters give an additional preference to their  
> second choice C.
> The votes are now:
> 49: A
> 25: B>C
> 26: C>B
> C is preferred to A by 51 votes to 49 votes. C is preferred to B by  
> 26 votes to 25 votes. B is preferred to A by 51 votes to 49 votes.
> C is now the Condorcet winner and therefore theRanked pairs winner.
> By giving a second preference to candidate C the 25 B voters have  
> caused their first choice to be defeated.


Pro-A is about equal strength with anti-A.  For this it makes sense  
for anti-A to give their side the best odds with the second vote  
pattern, not caring about LNH (B and C may compete with each other,  
but clearly care more about trouncing A).

An aside:  Note that the same strategy makes sense for IRV - A wins  
the first vote while B or C wins the second (C as shown; B with a  
trivial change in votes).

LNH may have made sense for the methods that inspired it, but cannot  
compete for causing trouble for Condorcet, considering IRV's problems.

Dave Ketchum

On Jan 17, 2010, at 2:30 PM, Chris Benham wrote:

> Abd Lomax wrote (17 Jan 2010):
>
> <snip>
>
> "Chris is Australian, and is one of a rare breed: someone who actually
> understands STV and supports it for single-winner because of LNH
> satisfaction. Of course, LNH is a criterion disliked by many voting
> system experts, and it's based on a political concept which is, quite
> as you say, contrary to sensible negotiation process."
>  <snip>
>
> I endorse IRV (Alternative Vote, with voters able to strictly rank  
> from the top however
> many candidates they choose) as a good method, much better than  
> Plurality or TTR,
> and the best of the methods that are invulnerable to Burial and meet  
> Later-no-Harm.
>
> Some of us see elections as primarily a contest and not a  
> "negotiation process".
>
> I endorse IRV because it has a "maximal set" of  (what I consider to  
> be) desirable
> criterion compliances:
>
> Majority for Solid Coalitions (aka Mutual Majority)
> Woodall's Plurality criterion
> Mutual Dominant Third
> Condorcet Loser
>
> Burial Invulnerability
> Later-no-Harm
> Later-no-Help
>
> Mono-add-Top
> Mono-add-Plump  (implied by mono-add-top)
> Mono-append
> Irrelevant Ballots
>
> Clone-Winner
> Clone-Loser  (together these two add up to Clone Independence)
>
> As far as I can tell, the only real points of dissatisfaction with  
> IRV in Australia are
> (a) that in some jurisdictions the voter is not allowed to truncate  
> (on pain of his/her
> vote  being binned as "invalid") and (b) that it isn't multi-winner  
> PR so that minor
> parties can be fairly represented.
>
> I gather the Irish are also reasonably satisfied with it for the  
> election of their President.
>
> <snip>
> "I've really come to like Bucklin, because it allows voters to
> exercise full power for one candidate at the outset, then add, *if
> they choose to do so*, alternative approved candidates."
> <snip>
>
> The version of Bucklin Abd advocates (using ratings ballots with  
> voters able to give
> as many candidates they like the same rating and also able to skip  
> slots) tends
> to be strategically equivalent to Approval  but entices voters to  
> play silly strategy
> games "sitting out" rounds.
>
> It would be better if 3-slot ballots are used, in which case it is  
> the same thing as
> (one of the versions of) "Majority Choice Approval" (MCA).
>
> IMO the best method that meets  Favourite Betrayal (and also the  
> best 3-slot ballot method)
> is "Strong Minimal Defence, Top Ratings":
>
> *Voters fill out 3-slot ratings ballots, default rating is bottom-most
> (indicating least preferred and not approved).
>
> Interpreting top and middle rating as approval, disqualify all  
> candidates
> with an approval score lower than their maximum approval-opposition
> (MAO) score.
> (X's  MAO score is the approval score of the most approved candidate  
> on
> ballots that don't approve X).
>
> Elect the undisqualified candidate with the highest top-ratings  
> score.*
>
> Unlike MCA/Bucklin this fails Later-no-Help (as well as LNHarm) so  
> the voters have a less
> strong incentive to truncate.
>
> Unlike MCA/Bucklin this meets Irrelevant Ballots. In MCA candidate X  
> could be declared the
> winner in the first round, and then it is found that a small number  
> of voters had been wrongly
> excluded and these new voters choose to openly bullet-vote for  
> nobody (perhaps themselves
> as write-ins) and then their additional ballots raise the majority  
> threshold and trigger a second
> round in which X loses.
>
> I can't take seriously any method that fails Irrelevant Ballots.
>
> Compliance with Favourite Betrayal is incompatible with Condorcet.  
> If you are looking for a
> relatively simple Condorcet method, I recommend Smith//Approval  
> (ranking):
>
> *Voters rank from the top candidates they "approve". Equal-ranking  
> is allowed.
> Interpreting being ranked above at least one other candidate as  
> approval, elect the most
> approved member of the Smith set (the smallest non-empty set  S of  
> candidates that pairwise
> beat all the outside-S candidates).*
>
>
> Chris Benham