[EM] Re: AWP versus DMC and AM

Chris Benham cbenhamau at yahoo.com.au
Thu May 5 11:09:52 PDT 2005

In this example of   James  G-A's:
26: A>>C>B
22: A>>B>C
19: C>B>>A
06: C>>B>A
22: B>C>>A
05: B>>A>C

Direction of defeats
A>C 52-48
C>B 51-49
B>A 52-48

Approvals: A48,  B46,  C47.

Originally, A was "Bush",  B was "Kerry" and  C was 
"Dean";  and  the 26 A>>C>B voters were presumed to be
 Burying B (i.e., sincere was A>>B>C).

You wrote (Thur.Apr.28):

>What happens if the 22 B>C>>A voters move the
approval cutoff upward,
>to get
>   22: B>>C>A
>You get
>    Approvals: A48, B46, C25.
>Consider the pairwise array with approval on the
>            A  B  C
>         A  48 48 52
>         B  52 46 49
>         C  48 51 25
>B is now the DMC (and MRAV/AM) winner.
>Even if the 19: C>B>>A voters moved their cutoff up
>as well, B would still win.
>This illustrates a Later-no-harm violation of the
>approval cutoff inDMC/AM: B- and C-preferring voters
>actually get the better effect of defeating A if they
>do NOT approve each other.

CB: Presumably you meant to write that those anti-A
voters *can*  "actually get the better effect of
defeating A etc." because you also wrote:

>B would also have been elected if the "6: C>>B>A"
>voters had moved their cutoff below B.
Leaving aside for the time being what we call it, the
property/criterion I think you are referring to could
be defined thus:
"If  x wins, and  afterwards some identical ballots
that approve x are uniformly changed only so that they
approve more candidates than previously; then if there
is a new winner it must be one of  the candidates
approved on these altered ballots."

Does  AWP  meet  this?  (James?).

Chris  Benham

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