[EM] Re: Later-no-harm, "Earlier-no-harm"

Chris Benham chrisbenham at bigpond.com
Sun Dec 28 11:03:02 PST 2003

On  Tue.Dec.23, 2003,  Kevin Venzke wrote:

"It's possible to define (a possibly limited version of) later-no-harm
as: "Adding strict preferences among candidates otherwise ranked last,
should not hurt the result of the election from the perspective of
this ballot."

(By this definition, however, Approval passes, since approving an
additional candidate doesn't just involve adding strict preferences,
but also deleting others.)"

Surely Later-no-harm is only applicable to ranked-ballot methods,and Approval
is not a ranked-ballot method. 
Other than trying to provide some ammunition for Approval versus IRV propaganda, 
is there any point to this new version?

On a posititive note, Kevin went on:
"I don't believe I've ever heard anyone suggest the obvious counterpart,
"earlier-no-harm:" "Adding strict preferences among candidates otherwise
ranked FIRST, (etc...)."

For example, if voting "A=B=C>D>E" gets me one of those first choices,
then voting "A>B>C>D>E" should not get D or E elected.

"Earlier-no-help" could also be defined.  If "A=B=C>D>E" elects D,
then "A>B>C>D>E" should not elect A."

I very much like the substance of this. On Mon.Dec.1,2003, I wrote:
"I think that it is absurd that half an even number of voters voting AB and the other 
half BA should have a different effect from all of them voting A=B, and also that it is 
unfair that a faction of voters who  support candidates A and B by all voting either 
AB or BA, should be in any way disadvantaged compared to a faction who support candidates 
C and D by all voting C=D."
The part after "and also.." I see as being equivalent to your "earlier-no-harm". I think 
I would sum up the idea behind your 2 "earlier-no-h..." criteria in a "Decisiveness Fairness
Standard" which says something like 
"a faction of voters who all vote a set of candidates over all other candidates should not be 
advantaged or disadvantaged by voting equal preferences (versus not)".
Have I been wrong to assume this is connected with Symetric Completion/fractional equal
Quoting Woodall (in the context of equal preferences not being allowed except for truncation),

"Symetric Completion.
A trucated ballot should be treated in the same way as its symetric completion. (The symetric 
completion of a ballot is obtained by replacing it by all possible completions of it with 
equal weight chosen so that the total weight is 1. For example,if there are five candidates 
a,b,c,d,e, then the symetric completion of a ballot marked ab consists of six ballots, each 
with weight 1/6, marked abcde, abced, abdce, abdec,abecd, and abedc.)"

Can a method meet Earlier-no-harm/help without complying with SC?

Chris Benham

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