[EM] How good can a method be?
nkklrp at hotmail.com
Fri Jan 16 01:57:02 PST 2004
>3. If more than 1 remain, apply Approval, electing the candidate above the
>most voters' Approval cutoffs.
>Chris Benham's suggestion would make sense here: any ballots that approve
>all or none of the remaining candidates could be minimally adjusted to
>make them relevant in step 3.
Absolutely. That hadn't occurred to me, but of course it should be done.
Smith Majority Approval meets wv's majority defensive strategy criteria,
while reducing other strategy incentives.
To meet those criteria with a pairwise-count method results in some
that are unavoidable for a good pairwise-count method. So I was interested
in finding other, nonpairwise-count ways of meeting those critreria, to
reduce those strategy needs.
Smith-Majority-Approval, though not entirely pairwise-count, is still mostly
pairwise-count (finding the Schwartz set and majority defeats). For that
reason it doesn't entirely get rid of those strategy incentives, but it does
Pairwise-count, with its accompanying additional minor strategy incentives,
is probably the only way to meet the majority defensive strategy criteria
with a method as simple as wv or Smith Majority Approval.
NES & DSV (batchwise and ballot-by-ballot) of course are not pairwise-count
methods. It's pretty much a sure thing that NES meets the majority defensive
strategy criteria, and I expect that DSV does also. So those are methods
that share wv's defensive strategy properties, but without the other
strategy incentives that are unavoidable when meeting those criteria with a
Though we on EM initially discussed offensive truncation, offensive
order-reversal, and defensive truncation as wv strategies, it turns out that
those are strategy possibilities that are present with all the best methods,
including wv, and anything better that is found. The defensive strategy
situation of wv can't be improved on. It will be the same with any best
It's always been a matter of how good a voting system can be. How much it's
possible to improve on wv. Very little, it turns out. A few unimportant
extra strategy incentives can be gotten rid of.
Apparently NES, and probably DSV too, are the ideal methods. Ideal because
they reduce strategy to its irreducible minimum.
How good can a method get? As good as NES & DSV.
Now, what pairwise-count strategy incentives am I referring to? Well, in the
wv vs margins debates, it was pointed out that, with wv, there can be
incentive to rank several of one's favorite candidates equally in 1st place,
even if one has perferences between them. For instance, if you believe, as I
do, that the candidates can be divided into 2 sets, such that the merit
differences within the 2 sets are negligibe compared to the merit difference
between the sets, then, with wv, it's to your advantage to rank all the
better-set candidates equally in 1st place. That's how I'd vote in a wv
I'm not criticizing wv. It's the best method (or class of methods) that's
been thoroughly studied & discussed. And what very little improvement on it
is possible is not possible with a comparably simple method.
I still advocate wv as the rank-count method to propose. SSD, MAM, or PC. It
probably isn't time to propose the fancier completely ideal rank-counts,
even if they'd been thoroughly studied & discussed. Maybe sometime later,
after wv has been in use, someone could eventually suggest a more
complicated ideal method.
The margins advocate who pointed out that strategy incentive seemed to
consider it a big problem. But I replied that it's only a strategy
"incentive", and not a defensive strategy need. No one needs to equal-rank
in order to protect majority rule or to protect the win of a CW. The only
situations in which a voter could benefit by the equal ranking would be in
certain special kinds of natural circular ties. So not only is it not a
defensive strategy need, but it isn't even an important incentive.
Most won't have incentive to do other than sincerely rank the candidates.
That's because most people don't seem to agree with me about those 2 sets.
(One way I word it is to say that the election has one or more completely
unacceptable candidates who could win). So, for instance, most progressives
won't feel that strategy incentive, and will feel free to sincerely rank the
candidates. Nader, Sharpton, Kucinich, Dean, [& the rest of the Democrats],
in order of preference, where I'd vote Nader & Sharpton in 1st place.
But, even for me, who'd vote according to that incentive in wv, I don't
consider it a problem. After all, the reason I'd vote that way is precisely
because I consider the better-set candidates relatively
uniform in merit.
Basically, I'd be using Condorcet as Approval. An Approval ballot perfectly
expresses the preferences of someone who consideres there to be just 2
merit-levels. And it quite adequately expresses the preferences of me, who
consider 2 merit levels to be the imiportant distinction.
The other wv strategy incentive that the margins advocates mentioned is even
If you have no preferences among your lower choices, wv gives you incentive
to randomly rank them, in order to give them more votes-against. It isn't
quite clear to whom that's supposed to be a problem. To the person who is
indifferent between those lower choices?
Not a problem. But, in any case, NES & DSV get rid of that unimportant
strategy incentive too.
Of course it isn't entirely true that, with wv, one should rank all the
candidates. That's because, with any method, even the best methods,
defensive truncation can be needed in order to deter offensive
order-reversal, if the electorate is sufficiently devious.
I hesitated to bring these subjects up, lest I make it sound as if wv has a
problem. I emphasize that wv's extra strategy incentives are nothing
compared to margins' unnecessary drastic defensive strategly needs, or those
of IRV. With wv there's no need for defensvie strategy unless someone is
attempting offensive strategy. That can't be said of margins or IRV.
I also hesitated to bring all this up because I was afraid that I'd restart
the wv vs margins debate.
But the topic of how good a method can be is interesting, and it requires
mentioning certain trivial, minor, unimportant, but avoidable strategy
incentives of the best simple rank-counts, the best rank-counts currently
being proposed, the wv methods.
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