# [EM] questions about IIAC & ICC

Markus Schulze markus.schulze at alumni.tu-berlin.de
Sun Jan 13 03:05:49 PST 2002

```Dear Mike,

you wrote (11 Jan 2002):

> But if IIAC, as Arrow intended it, isn't met by any method,
> then why wouldn't he mention that? If nothing meets IIAC,
> then there'd be no point in listing those other criteria,
> the ones in his impossibility theorem. If nothing meets IIAC,
> then why bother saying that nothing meets all the criteria
> in some list that includes IIAC? I really don't know of a
> method that meets that particular IIAC, and so I was just
> asking. If you know of one, tell me of it.

I have already mentioned in one of my last mails that there
are election methods that meet IIAC. I wrote (9 Jan 2002):

> Random Candidate meets "Independence from Irrelevant
> Alternatives" and violates "Independence from Clones".
> Tideman's Ranked Pairs method meets "Independence from Clones"
> and violates "Independence from Irrelevant Alternatives".

Also Random Dictatorship meets IIAC. So there are election
methods that meet IIAC.

******

You wrote (11 Jan 2002):

> How I define sincere voting?:
> A voter votes sincerely if s/he doesn't reverse a sincere
> preference or fail to vote a sincere preference that the
> balloting system in use would allow hir to vote in addition
> to the preferences that s/he actually did vote.
> Of course reversing a sincere preference means voting B over
> A when you prefer A to B. Voting a preference for A over B
> means voting A over B. You're then voting a sincere preference
> for A over B if you prefer A to B.

How do you define "sincere voting" for other election methods
than preferential election methods?

******

You wrote (12 Jan 2002):

> Most rank methods, even if monotonic, fail Participation &
> Consistency. Borda is the only rank method that I know to pass
> those 2 criteria.

All positional election methods meet monotonicity, participation
and consistency.

Markus Schulze

```