[EM] Approval vs IRV

[C.Benham]

Mike,

> Someone said that IRV lets you vote more preferences than Approval 
> does. But what good
> does that do, if it doesn't count them?

The term "count" here can be a bit vague and propagandistic. Also you 
imply that it is always better to "count" preferences (no matter how) 
than to not.

Also you seem to imply that all the voters care nothing about anything 
except affecting (positively from their perspective) the result and 
perhaps how their vote will do it. I reject that. A lot of voters want 
to know details of the result besides just who won, and want to see how 
some or all the candidates went, perhaps with the perspective of 
thinking about their voting strategy in the next election. And some 
people get some satisfaction from giving their full ranking of the 
candidates, even though most of that information will be ignored by the 
voting method algorithm.

As a thought experiment, consider this method: voters strictly rank from 
the top however many candidates they like and also give an approval 
cut-off, the winner is the most approved candidate, exact ties resolved 
by random ballot (doesn't matter if drawn ballot doesn't show approval 
for any of the tied candidates). After the election each candidates' top 
rankings scores (and preferably other voted preference information) is 
made known along with their approval scores.

I as a voter would happier with this than plain Approval. But I think 
after a while, say if the published results showed a failure of Majority 
Favourite, some voters might wonder why they have to gamble or use guess 
work in deciding where to put their approval cut-off and why the voting 
method can't use some algorithm that usefully uses more of the 
information on the ballots

> To say that IRV fails FBC is an understatement.
>
> IRV fails FBC with a vengeance.
>
> IRV thereby makes a joke any election in which it is used.


That is an exaggeration. Regarding the proper version of  IRV  I earlier 
defined (that allows voters to strictly rank from the top however many 
candidates they want), most of the time none of the voters
wouldn't even notice any  "FBC failure" (and so incentive to use the 
Compromise strategy).


> As I've already said, all it takes is for favoriteness-support to 
> taper moderately gradually away from the middle, something
> that is hardly unusual. Eliminations from the extremes will send 
> transfers inward to feed the candidates flanking a middle CW,
> resulting in hir elimination.


Yes, but if  the wing voters' pairwise preference for the middle CW over 
their opposite wing's candidate is weak, then arguably that doesn't 
matter much. Also, even though Approval has a strong centrist bias, it 
is possible that Approval will fail to elect a CW that IRV would have.  
After all, IRV meets Mutual Dominant Third and Condorcet Loser. (So for 
your example to work, the middle CW has to be solidly supported by fewer 
than a third of the voters).


> That said, though Approval or MTA is incomparably better than 
> Plurality, and would be completely
> adequate, I'd prefer, if electorally-attainable, a method that meets LNHa.


I like MTA and IBIFA (preferably with 4-slot ballots), and some of the 
Condorcet methods. I  wouldn't say that Approval would be "completely 
adequate" (but of course a big improvement on FPP).


Chris Benham



Mike Ossipoff wrote (1 Dec 2011):

Someone said that IRV lets you vote more preferences than Approval does. 
But what good
does that do, if it doesn't count them?

Approval counts every preference that you vote.

Since Approval doesn't let you vote all of your preferences, it doesn't 
count all of your
preferences. But, unlike IRV, you can choose which of your preferences 
will be counted.

You can divide the candidate-set into two parts in any way you choose. 
You, and only you, choose
among which two sets of candidates your preferences will be counted.

As I've said, our elections have completely unacceptable candidates. 
Under those conditions, most
methods reduce to Approval anyway. When, in Approval, you approve all of 
the acceptable candidates
and none of the unacceptable candidates, you're doing all that you'd 
want to do anyway.
---------------------------------------------------------------------------------
Yes, Approval has the ABE problem, the co-operation/defection problem.

We've discussed two solutions for that problem that could be used in 
Approval:

1. Your faction makes it known that they will, from principle, refuse to 
support some
inadequate alleged "lesser-evil" compromise. The other greater-evil-opposers
including the supporters of that "lesser-evil" will understand
that, if they need the votes of a more principled faction, and aren't 
going to get their
votes, then they had better approve that faction's candidates if they 
don't want a greater
evil to win.

Of course, no one who prefers your faction's policies to those of that 
"lesser-evil" would
have any pragmatic reason to approve the "lesser-evil" but not your 
faction's candidate.

2. Forrest proposed an ABE solution for RV, which involved calculating 
the correct fractional
support to give to the other greater-evil-opposing faction.

I'd like to add that, probabilistically, that method can be used in 
Approval.

In Forrest's example, where C is expected to get 49%, the A voters 
inform the B voters
that they will give to C 96% of full support in RV, or an RV 
middle-rating in an MTA-like system.

If the method is Approval, then the A voters tell the B voters that 
they're going to vote
for B with 96% probability. That will have the same effect as giving B 
96% support in RV.

The A voters would invite the B voters to do the same for them, of course.

Unlike solution #1, which is a bit confrontational, Forrest's fractional 
rating calculation
is quite diplomatic. "We're going to give you 96% support, and we 
suggest that you do
the same for us, in case it's we who are big enough to beat C with that 
amount of support.

As for implementation details, an A voter could put write the numerals 
from 1 to 10 on
identical rectangular pieces of paper, and put them in a bag. Then, 
twice (with replacement),
draw out a number, to make a completely random two-digit number.
If that number is less than 96, vote for B.

Or A voters could be advised to cube their street address, or the time 
of day expressed
in minutes, or the temperature, etc., and multiply by the square root of 
two, and then
write down the digits that are 3rd and 4th from the right.

Or A's and B's parties could have websites that use a pseudorandom 
number generator to
say "Vote for the other candidate" or "Don't vote for the other 
candidate", when someone
goes to the website and clicks on a button.

That said, though Approval or MTA is incomparably better than Plurality, 
and would be completely
adequate, I'd prefer, if electorally-attainable, a method that meets LNHa.

Mike Ossipoff