[EM] Ranked Preferences, example calculations

[Juho]

A general comment on this discussion thread.

I think what we would need here is few more well defined concepts to  
help us defining what we mean. The first term I'd like to see defined  
is a concept that I might call competitiveness. I have seen different  
people using different terms when referring to this or related concepts.

Competitive election is an election where voters do their best to  
make their side win. A non-competitive election is one where voters  
are just happy to express their opinions and then see who won (and be  
happy with whatever the result, with no interest to influence the  
outcome more than what they did when giving their genuine opinion).

One example from real life, asking some questions from a voter before  
the US presidential elections.
Q: Which of the candidates would be the best  president?
A: Independent candidate C.
Q: Whom are you going to vote in the elections?
A: Major party candidate A, since C has no chance of winning and A is  
a far better choice than B of the other major party.

Two very similar questions (who should be the president) with two  
quite different answers. In the first (non-competitive) case the  
voter just told her opinion. In the second (competitive) case it was  
obvious to her that she should not vote her favourite but she should  
maximise the effect of her vote.

Well, she could also have thought that this is how a two-party system  
works and how voters are supposed to behave. But in the second case  
she anyway probably felt that the other side is also going to do  
their best to make their candidate win, and so should she do as well,  
at least to balance the situation. She was thus competitive.

Maybe the definition above is not perfects. But I'd anyway like to  
see some stable definitions of this or related terms so that we could  
better discuss e.g. the characteristics of Range, Condorcet, Ranked  
Preferences etc.

It is typical to Range that it can behave in different ways in  
different situations, sometimes approximating Approval, sometimes  
using the different strengths in a more evenly distributed way.

Condorcet characteristically behaves in a relatively stable way in  
both competitive and non-competitive situations. It has however the  
known risks of strategic voting in some extreme situations (that I  
think are not that common in large public elections).

Juho Laatu



P.S. Another related concept and story just for your fun.

How to elect two candidates (using e.g. Condorcet):

Boxing team of two members
- elect the first member from A, B, C and D
- elect the second member from the remaining candidates using the old  
ballots (or by arranging a new election with new ballots)

Two colours in an advertisement
- elect one of the combinations of two candidates (AB, AC, AD, BC, BD  
and CD)

Elect a two-member team to represent our town in a meeting. Candiates  
are supposed to represent the whole city in a balanced way.  
Candidates A and B are democrats (55%). C and D are republicans (45%).
- don't use either of the methods above, use something proportional  
instead
- the likely outcome of either method would be election of two democrats

This is just to demonstrate that there are different methods for  
different needs, just like in the competitive vs. non-competitive case.

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