[EM] IIA Theory

[David Catchpole]

On Wed, 6 Oct 1999, Markus Schulze wrote:

> I prefer the following wordings:
> 
> Deterministic Independence from Irrelevant Alternatives:
> 
>    Suppose, that candidate A would have not been elected
>    if candidate B hadn't run. Then -if candidate B does run-
>    candidate A must not be elected.

This criteria loses ground in another three included "movements"
pertinent to IIA, though (?), with B staying, B leaving, A winning, A
losing. Maybe what we've found is four subdivisions of IIA? (for
deterministic- two stochastic). I like to think that the principle extends
to cases where the numbers of candidates winning may change itself, so
some assumptions of principle such as considering individual winners
become cumbersome for me.

>
> Stochastic Independence from Irrelevant Alternatives:
> 
>    Suppose, that candidate A would have been elected with
>    the probability p if candidate B hadn't run. Then
>    -if candidate B does run- the probability that candidate
>    A is elected must not be larger than p.
> 
> Markus Schulze
> 
> 
>