[EM] Does Droop give the same results as Hare?

[Donald Davison]

RE: [EM] Does Droop give the same results as Hare?

Dear James Gilmour,

Thank you for the effort you made to present us with this example of Hare
vs Droop.  The example tell us a number of things.

  First:  Your example tells us that you have answered the question, Droop
will not give the same results as Hare.  Of course, we already knew that.

  Second:  Your example tells us that you are a man of many hats.  Today
you are wearing your `Political Party' hat.  Most days you wear your
`Independent Candidate' hat (to show that you are a champion of the
independent candidate).

  Third:  Your example tells us that Droop will benefit the political
parties by averaging votes to protect party proportionality.  I already
knew that and I approve of protecting party proportionality in partisan
elections, but only in partisan elections (my new elimination rule should
replace the Droop quota, but that's another discussion).

In any non-partisan STV election the Droop quota should not be used because
every candidate is expected to stand as an independent candidate.  So, if
we were to make a second example by changing your example to a non-partisan
election then the quota to use should be the Hare quota and of course the
results will be different than your partisan Droop results.

Do you agree?  Answer while wearing your `Independent Candidate' hat.

By the way, if we were to work your example as Party List the results would
be three for Party A and two for Party B (same results as your Droop
results).

You could brag about Droop by saying that Droop STV will elect the same
candidates as Party List (Ha Ha).

Regards, Donald

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>Donald wrote:
>> There is the possibility that the Hare set of elected members
>> will be different from the Droop set of elected members.
>>
>> When this happens, the question must be asked:  `Which set of
>> members is the correct set of members to hold office?'
>>
>> The answer is the Hare set because the Hare set is more
>> proportional than the Droop set.
>
>To illustrate this point, I offer the following example:
>In an STV-PR election with 120 voters for five places, the HARE quota
>would be 24 votes (= 120 / 5).
>Suppose the election is contested by two parties (R and S) with three
>candidates each (A, B, C).
>With first preference votes as shown, Ra and RB would be elected at the
>first stage.
>
>Stage 1
>RA 24 elected   SA 19
>RB 24 elected   SB 19
>RC 16           SC 18
>     64               56
>
>Of the four continuing candidates, candidate RC has the fewest votes and
>so is excluded.  No matter
>what preferences are marked on those papers, SA, SB and SC will then be
>elected.
>
>Stage 2
>RA 24 elected   SA 19 elected
>RB 24 elected   SB 19 elected
>RC 16 excluded  SC 18 elected
>     64               56
>
>Applying the Hare quota, supporters of the larger opinion group (party),
>who constitute an absolute
>majority, elect only two candidates, while the smaller group elects three.
>
>
>For this election, the DROOP quota would be 20 = (120 / (5 + 1)).  With
>first preference votes as
>before, RA and RB would be elected at the first stage, each with a surplus
>of 4 votes above the
>quota.
>
>Stage 1
>RA 24 elected   SA 19
>RB 24 elected   SB 19
>RC 16           SC 18
>     64               56
>
>If we (reasonably) assume that these surplus votes transfer to the
>remaining candidate of party R,
>candidate RC will be elected, and SA and SB will take the two remaining places.
>
>Stage 2
>RA 20 elected   SA 19 elected
>RB 20 elected   SB 19 elected
>RC 24 elected   SC 18
>     64               56
>
>The outcome with Droop quota is that the supporters of  the larger group
>elect three candidates and
>the smaller group elects two.
>
>Perhaps Donald should reconsider the assertion he made above.
>Perhaps Donald should answer his own question: "You do support
>proportionality, don't you???"
>
>James [Gilmour]
>
>----
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