[EM] Scoring (was Re: OpenSTV 2.1.0 released)

[Michael Ossipoff]

I'd said:

> Do you claim that unimproved Condorcet can be
 > defended in a comparison with Symmetrical ICT, or ordinary ICT?

You replied:

Definitions of the methods needed in addition to their technical
properties. I don't exactly know what you mean with unimproved
Condorcet.

Unimproved Condorcet refers to what "Condorcet" meant before Improved
Condorcet was proposed by Kevin Venzke. In other words, unimproved
Condorcet is Condorcet that isn't Improved Condorcet.

Unimproved Condorcet is a broad category that includes every method
known as "Condorcet" before Improved Condorcet was proposed.

That includes Beatpath and all of the other Condorcet methods other
than Improved Condorcet.

When Kevin first proposed Improved Condorcet, he completed it with an
Approval count. So he called his proposed method
Improved-Condorcet-Approval (ICA).

Later, Chris Benham proposed Improved Condorcet completed instead with
a top-count. Using Kevin's naming system, I called Chris's method
Improved-Condorcet-Top (ICT)

Later, I proposed a modification of ICT that did the same improvement
at bottom end too. I call that Symmetrical ICT. It could be
abbreviated SITC.

Some criterion compliances:

A. Condorcet Criterion:

Here is a way to define the Condorcet Criterion:

A method passes if:

1. It collects ranked ballots. Unlimited rankings are allowed. Voters
may vote as many pairwise preferences as they wish.

2. If a candidate beats each one of the other candidates, then s/he wins.

[end of definition]


Unimproved Condorcet meets the Condorcet criterion if "beats" is
defined in the traditional way, whereby X beats Y iff more voters rank
X over Y than rank Y over X.

If the Condorcet Criterion is defined using a meaning of "beats" that
interprets equal-top ranking in the way that is consistent with the
preferences, intentions and wishes of the equal-top ranking voter,
then unimproved Condorcet fails the Condorcet Criterion, and ICT meets
that criterion

If "beats" is defined so as to interpret both equal-top and
equal-bottom rankings consistent with the preferences, intentions and
wishes of voters voting those rankings, then Symmetrical ICT is the
method that passes the Condorcet Criterion.


Preliminary definitions for the definitions of "beats"

(X>Y) means the number of ballots ranking X over Y
(Y>X) means the number of ballots ranking Y over X
(X=Y)T means the number of ballots top-ranking X and Y
(X=Y)B means the number of ballots bottom-ranking X and Y
.......You bottom rank a candidate if you rank hir over no one.

Definition of "beats" that isn't consistent with preferences and
intent of equal-top or equal-bottom ranking voter:

X beats Y iff (X>Y) > (Y>X)

Definition of "beats" that is consistent with preferences and intent
of equal-top ranking voter:

X beats Y iff (X>Y) > (Y>X) + (X = Y)T

Definition of "beats" that is consistent with preferences and intent
of equal-top ranking voter and equal-bottom ranking voter:

X beats Y iff (X>Y) + (X=Y)B > (Y>X) + (X=Y)T

Of course the reason why Symmetrical ICT meets the Condorcet Criterion
wherein "beats" is defined consistent with the preferences and intent
of the equal-top ranking voter and the equal-bottom ranking voter is
because Symmetrical ICT's definition uses that meaning for "beats".

But note that it is not a matter of re-defining CC so that SITC will
pass. It's a matter of defining CC consistent with interpreting a
voter's ballot consistent with hir preferences, intent and wishes.

B. Later-No-Harm (LNHa):

Condorcet methods, Approval, and Score fail LNHa.

But ICT and Symmetrical ICT don't fail it nearly as badly as does
unimproved Condorcet. In fact, I'll venture to say that ICT and SITC
don't importantly fail LNHa. Note that I'm not speculating about how
often they'll pass or fail. I'm saying that their failures aren't
important.That's because there isn't a chicken dilemma. Chicken
dilemma is the worst kind of LNHa failure.

C. Later-No-Help (LNHe):

Approval, Score, and Symmetrical ICT pass LNHe. Unimproved Condorcet
and ICT fail LNHe.

LNHe greatly simplifies u/a strategy. SITC's u/a strategy is as simple
as that of Approval and Score. In unimproved Condorcet, you won't know
what to do, even in a u/a election. I've recently told you why.

In ICT and unimproved Condorcet, u/a strategy calls for ranking the
unacceptable candidates in reverse order of winnability. That
incentive or need doesn't exist in Symmetrical ICT. In SITC, the u/a
strategy for unacceptables is to simply not rank them.

In (so far as I'm aware of) all rank methods that allow equal top
ranking, in a u/a election, there is a need to equal top rank the
acceptables. So, in ICT and SITC that is the u/a strategy. That need
exists in unimproved Condorcet too, but the problem is that moving
some particular acceptable to top can change the winner from an
acceptable to an unacceptable. That's why I say that, in unimproved
Condorcet, you won't know what to do, even in a u/a election.

D. FBC:

Approval, Score, ICT and SITC pass. Unimproved Condorcet fails.

E. Defection resistance:

...is had by ICT and Symmetrical ICT, but not by Approval, Score, or
unimproved Condorcet.

As I said, not a problem for Approval and Score (and probably not for
unimproved Condorcet either, for the same reason--though dealing with
it could be more complicated). But, as I also said, chicken dilemma is
the nearest thing to a problem that Approval has, and therefore you
don't significantly improve on Approval without getting rid of chicken
dilemma.

I'd said:

> The Chicken Dilemma is the nearest thing to a problem that
 > Approval has (though it's so well dealt with in Approval that it isn't
 > really a problem).

You replied:

I'm afraid it might be.

[endquote]

...except for the long list of reasons why it wouldn't be a problem,
the list that I've frequently posted during the past several weeks.

One of the defenses on that list was something that Forest suggested,
and which I call Strategic Fractional Ratings. You of course must have
missed my posting of that.

I've posted so much and so recently about the reasons why chicken
dilemma won't be a problem in Approval, and, posted specifically,
about SFR, that I don't think that I should repeat it again this soon.

On Fri, Sep 21, 2012 at 7:43 PM, Juho Laatu <juho4880 at yahoo.co.uk> wrote:
> We are about to dive into the details of some methods. I'm not sure if there are still some unanswered questions that I should cover, or my own claims that I did not clarify yet. I'll comment some random points below.
>
> On 22.9.2012, at 1.48, Michael Ossipoff wrote:
>
>> Maybe you meant to compare unimproved Condorcet to Approval (because
>> you didn't want to compare it to ICT and Symmetrical ICT).
>>
>> Ok. You mentioned the Chicken Dilemma. It exists in Approval and
>> Condorcet. Unimproved Condorcet doesn't get rid of the Chicken
>> Dilemma. It's basically the same in both methods.
>>
>> Approval meets FBC. Unimproved Condorcet fails FBC.
>>
>> Exactly how is unimproved Condorcet better than Approval?
>>
>> Condorcet's Criterion?
>>
>> Condorcet's Criterion compliance is meaningless when people are
>> favorite-burying.
>>
>> Then there's the matter of the highly computation-intensive count that
>> every rank method has, including the Condorcet methods.
>>
>> Computation-intensive, labor-intensive count = big count-fraud opportunity.
>
> It should be enough if you can record (digitally) the content of the ballots in a reliable way. >Computations should not lead to fraud since they can be easily double checked.

By whom :-)  With Approval, representatives of various parties are
observing a handcount in which approvals are tallied. The tallies are
added up at the conclusion of the count, in front of everyone.

In a rank method, what do you have? A digitally-recorded record that
will be checked...how and by whom? That's a problem even if storage
security is adequate (guards, locks, cameras, etc.)

Not quite the same thing.

You said:

If the content of the ballots is made public, checking is really easy.

[endquote]

Nonsense. How do you make public thousands or millions of rankings?
You could give copies to representatives of the parties (who trust the
copying process). But, for that matter, they also have to trust the
machine balloting and the process that made the rankings-record.

There are paper rankings store somewhere? See above.

>
>>
>> ...and it also means machine balloting and computerized count. That
>> means an even more greatly-enhanced count-fraud opportunity.
>
> Machine balloting is a risk in all methods

Not all methods have as much need for machine balloting.

You said:

 (if votes are only bits, and there is no paper copy). Also complex
ballots like ranked and rated ballots can be implemented on paper
quite well (= without too bad limitations). Computerized count is not
a problem if reliable source data is available for checks.

[endquote]

See above, about the checks of the stored ballots. And remember that,
with Approval, the tallying and the actual determination of vote
totals, can be done in front of everyone, during the public count.
Though ballots can still be stored, everyone has seen them tallied and
the tallies counted. Everyone has seen the answer determined.

You said:

 I stick to my comment on Condorcet methods (see above).

[endquote]

Stick away. Then, there's nothing more to be said. The arguments have
already been said, and can be compared, and their merits evaluated, by
anyone.

You said:

Maybe someone should arrange a real-life political Condorcet election
so we could see how extensive favourite burial there will be and how
much that will influence the results.

[endquote]

There isn't much information available about that, as yet. There have
been Internet polls, but how are we to know who is favorite-burying,
if we don't know who everyone's favorite is. I happened to observe the
Condorcet Internet voting of a friend whose preferences I knew. That's
an unusual exception. In that instance, she favorite-buried, ranking,
below all the Democrats, the candidate whose policies she preferred to
theirs.

I had another conversation with someone who insisted that approving
Favorite would count against helping Compromise outpoll Worst. Because
the method was simple Approval, it was possible to eventually show her
that how she rates Favorite has no effect on the result of approving
Compromise and not Worst. The lesson from that: People are inclined to
favorite bury, until you show them that there's no possible need to.
Because the method was Approval, I could show her that. I wouldn't
have been able to reassure her about unimproved Condorcet, because the
reassurance would be a lie.

With so few people I've spoken to about that, or observed voting,
those two are a very high percentage. Those two experiences, together,
would be quite unlikely if favorite-burial inclination weren't common
with new voting systems such as unimproved Condorcet.

You said:

Otherwise it seems to be just your guess against mine.

[endquote]

A fair and probable conclusion based on the available evidence.

But what if it were just guesswork? Does that mean that we should take
the guess that might cause widespread favorite-burial, and act on that
guess?

Look: Favorite-burial incentive, and the chicken dilemma, are so
easily avoided--why would you want to keep them (and then hope that
they wouldn't be a problem). It can be guaranteed that they won't be a
problem if they don't exist.

You said:

I don't believe that the existence of a (theoretical) FBC
vulnerability would automatically lead to widespread favourite
betrayal.

[endquote]

We've already been over that. It's easily demonstrated (I showed you
several times) that the typical Democrat voter votes as if s/he
regards elections as u/a, with Dem acceptable and Repub unacceptable.
It's been repeatedly shown to you that, with that person's beliefs and
assumptions, hir optimal strategy will include favorite-burial, if her
favorite isn't the Democrat.

What little evidence I've encountered revealed a favorite-betrayal
inclination in unimproved Condorcet, and even in Approval, till I
explained why it isn't needed. She eventually understood the
explanation, but didn't initially believe it. Favorite-burial
inclination, with new voting systems, including unimproved Condorcet
has been observed, in a high percentage of cases. For both of those
observations to be rare exceptions would be highly improbable.


You said:

Again I refer to Burlington IRV elections as an argument why this
probably would not happen even in the U.S. (The last sentence is about
the U.S. The others are generic.)

[endquote]

Municipal elections are nothing like presidential elections. A lot
more is at stake in a presidential election, or other election for
federal office.

Besides, IRV's FBC failure upset a lot of people, so much so that IRV
was thrown out.

Suppose they hadn't been allowed to throw IRV out. Do you think that
people wouldn't be shown the advantage of favorite-burial, from their
Burlington experience?

Mike Ossipoff