[EM] The Golden Rule of Preferences:

[Martin Harper]

Hi again Don: how are you today?

Donald wrote:

> Martin Harper <mcnh2 at cam.ac.uk> replied:
> "And what basis is this golden rule coming from? What makes it golden? What
> makes it better than an alternate rule: "earlier preferences are not to
> help or harm later preferences". Or, say, criteria such as monotonicity?"
>
> Donald: So, the Golden Rule upsets you,

Did I say that? For the record: the "Golden Rule" (aka Secret Preferences
Criterion aka SPC) does not upset me - I was asking questions because I'd like
to hear the answers.

> I should think it would, being as
> you are a promoter of Approval Voting, a method in which all the lower
> preferences will harm earlier preferences.

Since approval doesn't use ranked ballots, SPC doesn't really apply to it.
However, if you stretch the definition of SPC to cover approval, then you'll
find that it passes. Not that this matters until someone can tell us why we
should care about SPC in the first place.

> It's a good rule, you would do well to learn it and abide by it.

I'm not an election method, so SPC doesn't apply to me either. :-)

> From:  Stephen
>
>
> The "golden rule" gives  voters
> complete confidence to express their true preferences (as far as they feel
> able to) and, by doing so, to have as much influence over the composition of
> the elected body as possible.  If the "golden rule" does not hold fast under
> all circumstances, voters no longer have that complete confidence.

The golden rule does not give that complete confidence. A large number of
examples have already been given on the list where expressing your true
preferences in an IRV election will result in a worse candidate being elected,
from the point of view of that voter. The optimum strategy for IRV is often to
lie through your teeth. I'll be happy to send you relevant URLs if it would
help?

So I'll ask again: what is the basis behind "The Golden Rule" aka Secret
Preferences Criterion? what makes it a good rule to use to judge the relative
worth of election methods? What is your justification for it? Why should anyone
care?

Martin