[EM] Approval vs. IRV

[C.Benham]

Ted Stern wrote (29 Nov 2011):
 

> 47: A
> 05: AB (sincere is A>B)
> 41: B
> 07: BC
>
>  Approvals: B53,   A52,  C7
>
> I find this example contrived.
>
>  * If mass polling is available, many people will be aware of the
>    52/48 split between A and B ahead of time.
>
>  * Corruption is a separate issue.  With proper election funding
>    control, support for C would be restricted.


Ted,

I reject your criticisms of my example. Of course it's  "contrived". So 
what? How could it not be?

In my example "many people" as you say are "aware of the 52/48 split 
between A and B ahead of time".  95% of them vote as if they are aware 
of it.


> Approval-Bucklin (AKA ER-Bucklin) has the advantage in your contrived
> example of allowing the A > B voters to add B at a lower rank, which
> would not count unless neither A nor B achieves a majority.
>
> In many cases, it would not be necessary to rate candidates at the
> second (or lower) choice option, but having that option increases the
> available nuance of the vote.


Yes. My favourite similar methods are  IBIFA  and  MTA.

> However IRV does impose a false choice -- that you must rank your
> preferences separately, no equal ranks allowed.


In the case of methods that would fail FBC if they did allow equal-top 
ranking, I don't consider this to be a big deal. In the case of IRV, 
allowing it would make Push-over strategising easier and the method
more complex to count/implement.

> > In my opinion IRV is one of the reasonable algorithms to use with
> > ranked ballots, and the best for those who prefer things like
> > Later-no-Harm and Invulnerability to Burial to either the Condorcet
> > or FBC criteria.
>
> But are these the criteria we really want to achieve in a
> single-winner election?

Invulnerability to Burial is a very attractive property to me, but 
perhaps not.

> To say that LNH is the most important criterion is, at its most basic 
> level, an emotional argument.

I don't say that, but some people definitely like LNHarm. I prefer its 
LHHelp compliance, and regard its LNHarm compliance as only excusable 
because of it.

> I think what we really want to look for is a method that does a good 
> job of finding the candidate
> closest to the center of the electorate, while resisting strategic 
> manipulation.

I am mostly in sympathy with that aim.  Probably the best methods meet 
one of Condorcet and the FBC.

Chris Benham