[EM] Re: Woodall's DAC, Plurality

[Kevin Venzke]

Chris,

 --- Chris Benham <chrisbenham at bigpond.com> a écrit :
>> So the criterion means that if X is mentioned on fewer ballots than Y received
>> first-place votes, we can't pick X.  It sounds like a good criterion to me,
>> because it seems unlikely that, in this case, we could possibly have a good
>> reason, sufficient information, to think that X is a better pick than Y.

> CB: For the time being I am skeptical. I don't see why we need this as well as Monotonicity.

Markus gives this example in his paper:
11 AB
7 B
12 C

According to Plurality, A must not be elected.  Monotonicity may not be sufficient
here, because of the role B may play in deciding the winner.

> This is the first election-methods criterion that I have seen that employs the word/concept
> "probability". 

The term "probability" isn't necessary to define it.  As well, off-hand, Woodall's
definition of Participation uses the term, and Markus uses it in his definitions of
Monotonicity and Clone Independence, without using it to define Participation or
Plurality.

> I think that there might be a place for "Weak Monotonicity" as a fundamental
> standard for those who like to rigorously avoid any reference to sincerity/insincerity in
> their criteria. Something which just says that a candidate X generally placed higher on the
> ballots than candidate Y should have a greater probabilty of winning, just to knock on the 
> head any absurd method like "elect the candidate with the greatest number of second
> preferences".

Such a method would fail any definition of Monotonicity I've heard of.  Raising a
candidate to first place on some ballots could clearly make him lose.

Kevin Venzke
stepjak at yahoo.fr


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