[EM] Anyone got a good analysis on limitations of approval and range voting?

[robert bristow-johnson]

On Nov 29, 2009, at 6:37 PM, James Gilmour wrote:

>>> Robert Bristow-Johnson wrote (9 Nov 2009):
>>>
>>> "Of course IRV, Condorcet, and Borda use different methods  to  
>>> tabulate
>>> the votes and select the winner and my opinion is that IRV ("asset
>>> voting", I might call it "commodity voting": your vote is a
>>> "commodity" that you transfer according to your preferences) is a
>>> kabuki dance of transferred votes.  and there is an *arbitrary*
>>> evaluation in the elimination of candidates in the IRV rounds: 2nd-
>>> choice votes don't count for shit in deciding who to eliminate (who
>>> decided that?  2nd-choice votes are as good as last-choice?  under
>>> what meaningful and consistent philosophy was that decided?), then
>>> when your candidate is eliminated your 2nd-choice vote counts as  
>>> much
>>> as your 1st-choice."
>
> These statements suggest a misunderstanding of how STV voting works  
> and what preferences (US "rankings") mean in the STV voting
> system.

i know earlier someone (it might've been James, i dunno) wrote that  
"STV" (i think that's what it's called in Australia) is called "IRV"  
in the US.  i dunno to what extent that is true, but assuming it is,  
i understand exactly how IRV works as used by a few municipalities in  
the US, specifically what was used in Burlington VT which i think is  
identical to how it is in Cambridge MA, SF CA, someplace in NC, and  
Mpls/StP MN.  to how the method works in Australia, i do not know  
first hand.

also, i case you're interested, i voted for IRV for Burlington in  
2005 (it has been used in two elections since), and in the referendum  
it faces this coming spring, i'll likely vote against recalling  
(abolishing in favor of the FPTP/delayed_runoff we had before) IRV.   
the issue to me is that the single-transferrable vote (as done in our  
domestic IRV) is the wrong algorithm to tabulate the votes in a multi- 
candidate election where no candidate gets a majority of 1st-pick votes.

>   In all STV elections, the preferences are contingency choices.

that is true.  i fully support a contingency choice is multi-party/ 
multi-candidate elections.

>   Your vote is transferred to your second choice only in the
> event that your first choice cannot secure election or does not  
> need you support to secure election.

that is *one* way to use the information of the contingency choices.   
if you are working out a complex problem with multiple directions of  
interest (which an election with more than 2 sincere candidates would  
be), you don't necessarily quantify votes as a commodity with some  
fixed value, and then, as i still point out, transfer these  
commodities around according to a candidate viability metric that  
arbitrarily says that 2nd-choice is no better than the last choice.

you still haven't demonstrated why this contingent-choice information  
is the logical way to resolve a bunch of different competing  
contingency interests.  we know how, if there were only two  
candidates, to decide between the two (assuming they don't tie).  we  
know how to vote in that case (our sincere vote is the same as our  
tactical vote, easy), plurality = majority.  assuming no funny  
business, no one can dispute the popular legitimacy of the winner.

what we don't want to happen (assuming we want honest and democratic  
elections where tactical voting is not likely to work) is resolve an  
election differently between any two candidates differently than we  
would if those two were among a larger group of candidates.  we don't  
want to have to think how we would vote differently in the two  
cases.  if there is a Condorcet winner, and you are not that person,  
that Condorcet winner beat you, as far as the electorate is  
concerned.  if it was just the two of you, he beats you.  if it was  
you two along with N-2 other candidates, he still beats you (as well  
as beating everyone else).

> This is most easily seen in single-winner STV elections (US = IRV),  
> where the sequence of rounds is exactly analogous to the
> sequence of rounds in an exhaustive ballot (eliminating one  
> candidate at a time in successive ballots).

please don't patronize me.  there is nothing you're saying here that  
i don't know.  it is in how IRV does that that is the problem.  it  
doesn't accomplish the very goals we had when we adopted IRV (not  
rewarding tactical voting thus eliminating the need to consider  
tactical voting so we can vote the way we want to and not worry about  
contributing to defeating our own political interest - "voter regret").

>   The only difference is that
> in an STV (IRV) election you don't know what all the other voters  
> did in Round 1 when you come to give your second choice.

you mean you don't have transparency on how the rounds were performed  
or is it that your STV is a delayed runoff where you come in later?   
because i can't see the difference.  in the IRV i am familiar with,  
you order your candidates before knowing how any round turns out.  no  
one is returning to any polls.


>   So the
> preferences (= contingency choices) marked on an STV ballot are  
> quite different from the preferences marked on, for example, a Borda
> ballot where some attempt will be made to use all of the  
> information simultaneously.

as does Condorcet.  it doesn't matter what chronological order the  
computer uses to determine pairwise defeats.  the main difference  
between Borda and Condorcet is that Borda makes assumptions in  
quantifying contingency-choices (even if you think your 2nd-choice is  
almost as good as your 1st-choice and you think your 3rd-choice is a  
piece of crap, Borda doesn't know that and assumes your 2nd-choice is  
midway between your 1st and 3rd).

Condorcet only assumes that if you rank one candidate higher than  
another, that if the election was between the two in a 2 candidate  
race, you for vote for the candidate you marked higher.  is there  
anything arbitrary or unreasonably assumed in that?  and Condorcet  
says everybody's vote is of equal weight, even if you really, really,  
really like your guy and i only sorta prefer my guy.  if the election  
was only between your guy and my guy, our votes would have equal  
weight and together would cancel each other's effect.

> The same applies to STV multi-winner elections (STV-PR),

i haven't taken on the issue of multi-winner elections, at all.   
single-transferable vote might be fine for multiwinner elections (we  
have that in Burlington VT, too, with our state senators), but even  
if it's best for multi-winner does not mean it's best for single- 
winner.  it's possible (there could be little cycles) to order  
candidate preference in a Condorcet fashion, like if there was a  
single beat-path (sounds less likely) and pick the top N candidates  
to fill N seats.  but i don't (yet) advocate a method different than  
single-transferable vote for multi-winner elections.

--

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."