[EM] Approval vs IRV

[MIKE OSSIPOFF]

Of course it's true that it's at least a near toss-up between IRV & Runoff. 
But that isn't the case with Approval vs IRV.

IRV can claim two criterion compliances over Approval:

1. Mutual Majority Criterion (MMC)

2. Indepence from Clones Criterion (ICC)

I've pointed out here many times why those criteria don't mean anything for 
IRV against Approval, because the examples where IRV looks better by those 
criteria are also examples in which IRV, but not Approval, fails other 
criteria that are more general in their applicability. WDSC & FBC.

As I was saying before, I often call MMC the "Fortuitous Special Case 
Criterion), because it only applies in what, for a certain set of voters, is 
a fortuitous special case. But that case isn't so fortuitous for other 
voters, and every example of that type leads to an IRV failure example for 
WDSC & FBC.

So, if an IRVer would like to say that the IRV failures that some of us have 
been describing are rare, then how do they explain their presence whenever 
they write an example where IRV does better than Approval by MMC or ICC?

A clone set preferred, by a majority, to other candidates is also a mutual 
majority set.

Wouldn't it be nice if all spoilers were clones, or mutual majority 
candidates. In general, they aren't, and then ICC & MMC don't apply.

As I was saying before, WDSC says that a majority who prefer X to Y should 
have a way of making Y lose, without having to reverse a preference. No 
special stipulations about a clone-set or mutual majority.

Likewise, FBC says that no one should have need to bury their favorite, with 
no stipulations about clone sets or mutual majorilty.

Here's how I've lately been wording FBC:

For a particular election, and for a particular voter who has a unique 
favorite, there shouldn't be any configuration of other people's ballots 
such that that voter can optimize hir outcome in that election only by 
voting someone over hir favorite.

A voter optimizes hir outcome in an election, with a particular 
configuration other voters ballots, if s/he gains an outcome to which s/he 
doesn't prefer any other outcome that s/he could have gotten by voting a 
different way in that election with that configuration of other voters' 
ballots.

[end of FBC definition]

This definition is more lenient than Alex's definition, which involves 
incentive. But IRV still fails. Approval and CR pass.

The criteria that Approval passes and IRV fails are more generally 
applicable.

Sure, Chris can probably find some silly Woodall criteria that IRV meets, 
such as LNH. Because IRV eliminates your favorite before it lets you help 
anyone else, therefore helping someone else can't hurt your favorite 
(because IRV has protected your favorite by eliminating hir). And adding 
someone to your ranking not only won't help your favorite, but it will very 
likey be ignored by IRV. An ignored ;preference can't help that candidate. 
IRV capriciously recognizes some voted preferences and ignores others.

I sometimes ask: What would you say about a manager who makes irrevocable 
decisions based on a tiny fraction of the available information? That's what 
IRV does.

It's true that Approval doesn't let us vote all of our pairwise preferences, 
as IRV does. But Approval, unlike IRV, reliably counts every preference that 
you consider important enough to be one of those that you vote. Approval 
lets you choose which of your pairwise prefefrences will be counted. IRV 
chooses capriciously for you.

In Approval, people will typically be voting about half of their pairwise 
preferences.

And before someone argues that WDSC & FBC aren't to be found in journal 
articles, I suggest that criteria be judged on their own merits.  Millions 
of voters are cowed by the lesser-of-2-evils problem, so that they bury 
their favorite because of it. It matters what a majority has to do in order 
to make a greater-evil lose. It matters to those millions who are going to 
bury their favorite in November for that purpose.

Mike Ossipoff

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