[EM] Absolutely new here

[Kristofer Munsterhjelm]

On 06/16/2013 05:26 AM, Benjamin Grant wrote:
> I just started trying to wrap my brain around all the ins and outs about
> voting methods, and I wanted to check two things with my elders (on this
> subject):
>
> 1)As far as I can see, the reason IRV has some strange/unusual results
> is because it is absolutely critical what order you eliminate
> candidates. So an election where Voting Bloc 1 has a 13% share of the
> ballots and Voting Bloc 2 has a 16% share of the ballots can utterly
> flip around using IRV if VB1 goes up two points and VB2 goes down 2.
> Because with IRV, the order of elimination is really the first-most
> deciding factor in who wins.

[snip]

> A few percent either way on the last line changes **everything**.
>
> This seems to be a flaw with IRV, yes? It is “too sensitive” on small
> changes because they can change the order of elimination.

Yes. Like a chaotic process such as a fractal, it exhibits sensitivity 
to initial conditions. Reiterating an IRV round can draw similar points 
very far away from one another, and on some level, it feels similar to 
the kind of effects you get by say, reiterating the Henon function on 
two close points until they're no longer close at all.

You can see some visualization of this phenomenon here: 
http://zesty.ca/voting/sim/

> 2)I haven’t seen a voting system like this – what are the issues with
> it? Upsides and downsides?
>
> A)Each voter ranks their choices on their ballots, first through last place.
>
> B)If one candidate got a majority of 1^st place votes, they win. If not,
> the second place votes are added. If still no majority he third place
> votes are added, and so on, until one candidate has a majority.
>
> Would the above system work?

That's Bucklin. http://en.wikipedia.org/wiki/Bucklin_voting . It's one 
of the few ranked methods that have been used in political elections in 
the United States, and it has a connection to median rating (which 
elects the candidate with highest median rating or grade).

It would work, but the rating variant is better. In the context of 
ranking, Bucklin fails Condorcet, for instance.

It also has some bullet-voting incentive. Say that you support candidate 
A. You're reasonably sure it will get quite a number of second-place 
votes. Then even though you might prefer B to A, it's strategically an 
advantage to rank A first, because then the method will detect a 
majority for A sooner.

One of the points of the graded/rated variants is to encourage the 
voters to think in absolute terms ("is this candidate good enough to 
deserve an A") rather than relative terms ("is this candidate better 
than that candidate"). If they do, then the method becomes more robust.

> Thanks, very new to all these considerations, still trying to learn the
> names of the different methods as well as the names and meaning of the
> different criteria like Condorcet, Later No Harm, etc.

Alright. If you have more questions, just ask!