[EM] Richard's criteria
MIKE OSSIPOFF
nkklrp at hotmail.com
Thu Feb 12 04:02:02 PST 2004
Richard said:
Any of the strategic criteria on the electionmethods.org site can be
defined without reference to "sincere preferences" or "favorites".
I reply:
Thank you Richard. I said several days ago that all 4 majority defensive
strategy criteria can be written without mentioning preferences or sincere
voting. But thanks for repeating it.
When I made that startement, I gave an example, a votes-only equivalent to
my Condorcet Criterion.
The only new part of your claim is that FBC can be written votes-only. A few
days ago I asked how that could be done. Maybe you've done that, maybe not.
More about that at the FBC part of your posting.
Richard continued:
Here are my "votes-only" definitions:
SFC: If X beats all other candidates in pairwise comparisons, and
a majority of ballots rank X over Y, then Y does not win.
I reply:
If, as seems to be the case, based on how it's written, that criterion
applies only to rank methods, then, for that reason, it isn't equivalent to
SFC.
If "ranks X over Y" means "votes X over Y", then Plurality meets that
criterion. So it isn't equivalent to SFC.
Richard continued:
GSFC: If X is in the Smith set and Y is not, and a majority of ballots
rank X over Y, then Y does not win.
I reply:
Same answer as for SFC.
Richard continued:
SDSC: For any combination of N ballots that all rank candidate X over
candidate Y, and any other combination of M ballots, if N is greater
than M, then Y does not win the election when the two groups of
ballots are combined.
I reply:
Same answer as for SFC & GSFC. There are methods other than rank methods.
SDSC applies to all proposed methods, and probably to any proposable method.
SDSC doesn't just apply to rank methods. And if "ranks X over Y" means
"votes X over Y", then Plurality passes your "SDSC".
Richard continued:
Note: The statement in the electionmethods.org commentary that
"Compliance with SDSC means that a majority never needs any more than
truncation strategy to defeat a particular candidate" is puzzling
(truncation strategy is "falsely voting two candidates equal", is it
not?).
I reply:
No it is not. If you don't include certain candidates in your ranking, then
you aren't voting for them. If you aren't voting for them, then there isn't
a compelling case that you're voting them any way, including equal. You're
leaving them out equally.
Of course by my definition of a voted pairwise preference, you're making a
voted pairwise preference for X & Y even if you don't rank either.
So, to avoid the above objectino, it would be better if we stated, with
SDSC, a supporting definition of voting 2 candidates equal.
We've answered that question a number of times. We'd have clarified the
definition of voting 2 candidates equal, at the website, but that was felt
to unnecessarily lengthen the SDSC definition. It seems to me that we should
add to the SDSC definition a definition of voting 2 candidates equal.
As I've said, the electionmethods website is a committee project, and
committee projects don't always go the way that some particular committee
member would like. Some say that our definitions should give up some
precision in order to be briefer or more simply worded. Some supporting
definitions have been left out for brevity. The definition of voting 2
candidates equal is one of those that was left out. I'll suggest to Russ
that we include it.
A voter votes X equal to Y if s/he doesn't vote X over Y, and doesn't vote Y
over X, and votes X over someone, and votes Y over someone.
[end of definition of voting X over Y]
If you don't rank someone, it's reasonable to say that you aren't voting for
them. If you disagree, how serioius a quibble is that really?
Richard continued:
Also, the statements in the commentary about "countering
offensive order reversal" are completely irrelevant, since the need
for defensive strategy is based on the opposing votes cast regardless
of whether those votes are the result of offensive order reversal.
I reply:
It isn't quite clear why Richard thinks that the fact that the fact that
sincere votes can have the same effect as similarly voted strategic votes
means that it's irrelevant to speak of countering offensive order-reversal.
Is it meaningless to speak of blocking an intentional punch because someone
could also hit you accidentally, and that would be blocked too, by the same
block?
1. Sometimes it's desired to counter offensive order-reversal.
2. The strategies that we've described for countering offensive order
reversal do indeed accomplish
that purpose.
The fact that someone could sincerely vote the same way as an offensive
order-reverser is "completely irrelevant", to use Richard's own words.
Richard continues:
WDSC: For any combination of N ballots that all rank candidate X equal
to or higher than candidate Y, and any other combination of M ballots,
if N is greater than M, then Y does not win the election when the two
groups of ballots are combined.
I reply:
Same answer as for SFC, GSFC, & SDSC. WDSC doesn't apply only to rank
methods. And if we take "rank X over Y" to mean "vote X over Y", then
Plurality passes Richard's "WDSC".
Richard continued:
FBC: For some set S of ballots, if R is the set of results that can
occur when ballot B is added to S if candidate X is given the highest
ranking on B, and R' is the set of results that can occur if ballot B
is added to S when candidate X is not given the highest ranking on B,
then either X is a member of R, or R' is a subset of R.
I reply:
I asked how a votes-only FBC equivalent could be written. Your criterion may
or may not be equivalent to FBC. From your other criteria in your posting,
I'd say the likelihood isn't promising.
In any case, FBC is written in a way that clearly, directly & obvioiusly
speaks to a voter concern.
Why would anyone want to write it as Richard has written here (even if
Richard's criterion is equivalent to FBC)?
The above "FBC" wouldn't be publicly usable. If I tried, everyone would tell
me they have no idea what it's supposed to mean. And even for someone who
knows what it means, it doesn't speak directly, obviously and clearly to
voter concerns as my own version of FBC does.
So, even if it should turn out that Richard's "FBC" is equivalent to FBC, I
wouldn't adopt it or replace FBC with it.
Mike Ossipoff
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