[EM] Proportional multi-winner ranked voting methods - guidelines?
electionmethods at votefair.org
Sun Feb 26 21:00:17 PST 2017
On 2/23/2017 10:43 AM, James Gilmour wrote:
> Please see the attached results of some STV-PR elections
> to the Northern Ireland Assembly.
> If Canada had results like those from its Federal and
> Provincial elections no-one would be calling for
> electoral reform in Canada.
The referenced data supports my belief that the number of seats per
district is heavily correlated with the number of popular political parties.
In this case there are 6 seats per district, and there are about 6
popular political parties. Specifically the political-party count
includes 4 popular parties that apparently fill the first 4 seats, and
then another 4 mid-popular parties that compete for the next 2 seats (in
each district). (The least-popular parties rarely get seats.)
Although in this case the correlation -- between seats per district and
number of popular political parties -- is a simple correlation, other
correlations are possible.
As a hypothetical example, if there were 5 seats per district, two
dominant political parties might typically win the first four seats (two
seats per party), and less-popular parties might often win the remaining
5-th seat (with different parties winning in different districts).
The more political parties there are, the messier it is to create a
ruling coalition that really represents what the voters want. Too often
a coalition compromises on issues that are most important to the voters
in those parties. If anyone doesn't understand this disadvantage of
needing coalitions, which I've explained before, please ask.
One of the advantages of VoteFair ranking is that it favors fewer
political parties in order to let the voters form their own coalitions
-- in the form of very popular political parties. Yet the method allows
as many parties as the voters really want.
VoteFair ranking accommodates as many parties as possible, yet limits
the number of candidates in each race. Here is how:
* In every election the popularity of parties is re-measured, and the
popularity rankings are used in the next election.
* Each of the two most popular parties can offer two candidates (per party).
* The mid-popular parties can offer just one candidate each.
* The currently least-popular parties are not allowed to offer any
candidates in the race -- in that district, based on party popularities
within that district. (The popularity of parties can vary from district
to district, and only that district's popularity rankings are used for
* The limited number of candidates allows voters to get to know these
candidates better, which is important for ranking them meaningfully
(without saying "after my first and second choice I have an equal
dislike for the remaining candidates").
In a sense, VoteFair ranking does the opposite of what closed-list PR
does. Closed-list PR gives control to party leaders, instead of giving
control to the voters. In contrast, VoteFair ranking gives control to
the voters, so that "insider" candidates (who are liked by party
leaders) cannot get elected -- to either the district seats or the
nationwide seats -- unless they are ALSO the most popular candidates
according to the voters.
The latest development in the U.S. Democratic party serves as an example
of the unfairness of a party being controlled by insiders, rather than
voters. Specifically the new chairperson of the Democratic party was
the insider favorite. Most Democratic voters would have preferred the
candidate who was favored by Bernie Sanders and Elizabeth Warren, who
the voters prefer as the most popular Senators in the Democratic party.
Since the above PR-related comments are about closed-list PR, I'll add
that open-list PR is better, yet it uses single-mark ballots, which are
vulnerable to tactics that take advantage of vote splitting.
Another important point about STV is that it fails to consider all the
preferences of all the voters. Instead, like IRV, it is based on the
mistaken belief that the candidate with the most currently-first-choice
"votes" is most popular, and the candidate with the fewest
currently-first-choice "votes" is least popular. This flaw makes it
easier for the "wrong" (less-popular) candidate to win a seat.
This flaw was recently demonstrated in the U.S. Republican presidential
primary election, where single-mark ballots were used and there were
more than a dozen (12) candidates. The more candidates there are in a
race (not counting the ones who get very few votes), the more dramatic
this unfairness can be.
Expressed another way, the first priority should be to fill seats with
the most popular candidates, and the second priority should be to get
some degree of proportional results for the remaining seats.
VoteFair ranking follows this prioritization. Specifically:
* 1-2-3 ballots and pairwise counting are used to fill the first seat in
* The second seat in each district is filled by the most popular
candidate (using 1-2-3 ballots and pairwise counting) after
proportionally reducing the influence of the voters who are already
well-represented by the first-seat winner.
* Some remaining "nationwide" seats are allocated to political parties
based on the voters' party preferences (i.e. voters rank political
parties and the first choice is used for this purpose). The nationwide
seats are filled with candidates who were the most popular (in their
party) within their district (but failed to win a district seat), and
who got the most support when compared across district boundaries.
This approach is much fairer than allowing parties to choose their
In particular, it defeats the strategy of each party offering just one
"insider" candidate. (The second candidate from the same popular party
is optional, but a popular party that does not offer a second candidate
will become less popular because the manipulation becomes obvious.)
To repeat my original key point, any voting method that only looks at
one voter's currently-top candidate at a time cannot produce fair
results. Fair results can only be assured if all the preferences of all
the voters are considered pairwise (not simplistically one-at-a-time).
Just hiding the unfairness -- by making adjustments according to
political-party "quotas" -- is not solving the underlying unfairness.
Yes, proportionality is desireable, but not at the expense of ending up
with less-popular candidates.
Both can be achieved, but:
* PR sacrifices fairness by not providing a fair way to control which
candidates win each party's seats.
* STV sacrifices fairness in several ways:
** Through its counting method.
** Through what I'll call "round-off errors" if it is used to fill more
than 2 seats per district (and if the number of seats does not happen to
match the current number of popular political parties).
** It does not handle adjustments in "nationwide" seats, after the
round-off errors have accumulated over all the districts.
Questions? Please ask.
On 2/23/2017 10:43 AM, James Gilmour wrote:
>> Richard Fobes (VoteFair) Sent: 23 February 2017 17:54
>> However, as I stated before, STV would not provide fair results if it were used for a full national legislature.
>> Recently, in Canada, some people have been promoting the idea of using STV to elect about 5 MPs (members of parliament) from
>> each district (which they call a "riding"). That would produce very unfair results!
>> That's what I had in mind when I referred to using STV repeatedly.
> Please see the attached results of some STV-PR elections to the Northern Ireland Assembly.
> If Canada had results like those from its Federal and Provincial elections no-one would be calling for electoral reform in Canada.
> James Gilmour
> Edinburgh, Scotland
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