W3C Advisory Committee Meeting, May 2018

1. STV
Explained
Hold onto your hats, we’re in for a wild ride.
Natasha Rooney
@thisNatasha
nrooney@gsma.com
Q1
�

2. There is no perfect
voting system.
Disagreers must state their supported “perfect” system.

4. STV
Single Transferable Vote
Single vote, which transfers between candidates which you
rank in your order of choice
Q2
�

5. STV aims for
Proportional
Representation

6. STV aims for
Proportional
Representation

9. STV aims to
Reduce
Wasted Votes

10. STV can be used for
Single winner
elections
Multi winner
elections
Q3
�

11. STV
Phases
1. Vote
2. Count
HARD
EASY

12. Stage 1:
Vote

13. In STV, you
have 1vote.
Q4
�

14. Example Election
Nakamura
Rosie
Li
Karl
Adele
3 AB Seats
EXAMPLE:
5 Candidates
3 AB Seats

15. 1 Vote, Ranked Candidates
Nakamura
Rosie
Li
Karl
Adele
Ranking Candidates
When you “Rank Candidates” you are
stating the order you want your vote
to be assigned and transferred.
EXAMPLE:
5 Candidates
3 AB Seats

16. Rank Candidates
Nakamura
Rosie
Li
Karl
Adele
2
3
1
5
4
- Li is is my first choice for AB
- If Li is elected or eliminated
and another seat is still available,
I want my vote to transfer to
Nakamura
- If Nakamura is elected or
eliminated and another seat is
still available, I want my vote to
transfer to Rosie
- If Rosie is elected...
EXAMPLE:
5 Candidates
3 AB Seats

17. Rank Candidates
Nakamura
Rosie
Li
Karl
Adele
2
3
1
5
4
- Li is is my first choice for AB
- If Li is elected or eliminated
and another seat is still available,
I want my vote to transfer to
Nakamura
- If Nakamura is elected or
eliminated and another seat is
still available, I want my vote to
transfer to Rosie
- If Rosie is elected...
EXAMPLE:
5 Candidates
3 AB Seats
ALERT: vote transferral isn’t
quite that easy!

18. Not Ranking All Candidates
Nakamura
Rosie
Li
Karl
Adele
2
3
1
4
EXAMPLE:
5 Candidates
3 AB Seats

19. Stage 2:
Count

20. Stage 2:
Count- Make a quota
- Counting rounds begin
- Declare winners who reach quota, or remove least popular
- Transfer votes
- Repeat until all seats are full.
Q5
�

21. Quota: Droop Method

22. Making our Quota
Nakamura
Rosie
Li
Karl
Adele
105 Votes (105 Voters)
5 “Bad” votes
3 AB Seats
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26

23. Voters, Votes and Bad Votes
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)

24. Voters, Votes and Bad Votes
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
VALID VOTES = 100

25. Quota: Droop Method
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26

26. Votes
Li
Rosie
1
2
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Adele
Karl
1
2
15
Q6
��🇳

27. Rounds
Li
Rosie
1
2
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 1
Candidates ranked “1”
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Li 35
Rosie 20
Nakamura 25
Adele 15
Adele
Karl
1
2
15
Li is the only candidate
over the quota!
Li GETS SEAT!
WINNERS:
Li

28. Rounds
Li
Rosie
1
2
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 1
Candidates ranked “1”
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Li 35
Rosie 20
Nakamura 25
Adele 15
Adele
Karl
1
2
15
Li had 9 votes over the Quota
Her 9 votes are transferred to her
voters second choice
In our SIMPLE example all Li’s
voters voted Rosie second
Rosie gets 9 more votes
WINNERS:
Li

29. Rounds
9
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 2
First vote transfer
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Rosie 29
Nakamura 25
Adele 15
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Li
Rosie2
1
Rosie is the only
candidate over the quota!
Rosie GETS SEAT!

30. Rounds
9
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 2
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Rosie 29
Nakamura 25
Adele 15
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Li
Rosie2
1
Rosie is the only
candidate over the quota!
Rosie GETS SEAT!
Rosie had 3 votes over the Quota
Her 3 votes are transferred to her
voters next choice
All Rosie’s remaining voters voted
Adele second
Adele gets 3 more votes

31. Rounds
35
Rosie
Adele
1
2
3
Nakamura
Karl
1
2
25
Round 3
No Candidate meets the
Quota. Candidate with
the fewest votes
eliminated.
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Nakamura 25
Adele 18
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Li
Rosie2
1
Adele’s new total for Round 3 is 18
Nobody meets the quota
Adele has the lowest votes as is
eliminated.
Adele is ELIMINATED
Q7
��

32. Rounds
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 4
No Candidate meets the
Quota. Candidate with
the fewest votes
eliminated.
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Nakamura 25
Adele 18
Karl 15
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Li
Rosie2
1
Adele’s votes are transferred to her
voters next preferred candidate
In our SIMPLE example 15 of
Adele’s remaining voters next
choice is Karl
Karl is added to the count!

33. Rounds
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 4
No Candidate meets the
Quota. Candidate with
the fewest votes
eliminated.
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Nakamura 25
Karl 15
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Li
Rosie2
1
Karl is added with 15 votes
Nobody meets the quota
Karl has the lowest votes as is
eliminated.
Karl is ELIMINATED

34. Rounds
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 5
Process repeats until
seats filled or candidates
remaining is the same as
the number of seats.
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Nakamura 25
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Nakamura
Li
Rosie2
1
Nakamura remains with less votes
than the quota.
But he is the only candidate
remaining.
Nakamura GETS THE
LAST SEAT!

35. Happy Voters?
Li
Rosie
1
2
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Nakamura
�������
WINNERS:
Li, Rosie, Nakamura

36. STV
is a “family” of
voting systems.
Q8
�

37. - Quota Calculation
- Transfer Method

38. Quota Calculation Droop: no more candidates than seats
to be filled.
Hare: simpler and typically produces
same results as Droop but is kinder to
smaller groups and therefore
differences in final seat allocation.

39. Rounds
Li
Rosie
1
2
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Round 1
Candidates ranked “1”
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Li 35
Rosie 20
Nakamura 25
Adele 15
Adele
Karl
1
2
15
Li is the only candidate
over the quota!
Li GETS SEAT!
WINNERS:
Li

40. 2 types of transfers
1. From Elected candidates
2. From Excluded candidates

41. Transfer Methods
- Random: Yup.
- Wright: Uses ratios to transfer votes to each
voter's next preferred hopeful. Manual counting
takes a long time.
- Hare-Clark: transfer fraction of votes at full
value
- Gregory: eliminates randomness. Transfer all
votes at a fractional value.
Counting methods can suffer from
recursion, as votes get moved back to
an already chosen candidate, then
back to a new winner...
Rosie
Karl
1
2
30
Karl
Rosie
1
2
30

42. Q9
Transfer Method: Meek
Algorithm designed to
stop recursion
- Winning candidates continue to
receive votes
- Winning candidates will continue
to transfer surplus votes
throughout the counting
- Count must be done by software.
Features
- Each candidate is “Hopeful”,
“Elected”, or “Excluded”
- Weighting (Keep Factor)
- Winners keep fraction of their
received votes, remaining vote
fractions get transferred to other
candidates.
- Quota changes throughout

43. Counting using Meek
Li
Rosie
1
2
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Adele
Karl
1
2
15
R Li Rosie Nakamura Adele Karl
1 35
li = 1
20
r = 1
25
n = 1
15
a = 1
0
k = 1
2 25.9 = 35 * li
li = 0.74
29.1 = 20 + (1 - li) * 35
r = 1
25
n = 1
15
a = 1
0
k = 1
3 li = 0.74
(Prev li * Q / Prev V)
20
r = 0.8
25
n = 1
17.86 =
15 + (1 - li)*(1 - r) * 35
(1 - li)*(1 - r) * 20
a = 0
0
k = 1

44. Transfer of Votes
from Eliminated
Candidate Methods
- Single transaction: Transfer all votes without
segmentation.
- Segmented distribution: Split into segmented
transactions.
- Value based segmentation: Each segment
includes all ballots that have the same value.
- Aggregated primary vote and value
segmentation: Separate the Primary vote
(full-value votes) to reduce distortion and limit
the value of an elected transfer.
- FIFO (First In First Out – Last bundle):
Distribute each parcel in the order in which it
was received.
- Iterative count: reallocate the loser's ballots and
restart the count.
- Bulk exclusions: any candidates with a tally less
than a breakpoint can be included in a bulk
exclusion process.

45. Votes
Nakamura
Karl
1
2
30
Rosie
Karl
1
2
20
Li
Adele
1
2
25
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Adele
Karl
1
2
15

46. Rounds
Round 1
Candidates ranked “1”
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Nakamura 30
Rosie 20
Li 25
Adele 15
Nakamura is the only
candidate over the quota!
Nakamura GETS
SEAT!
WINNERS:
Nakamura
Nakamura
Karl
1
2
30
Rosie
Karl
1
2
20
Li
Adele
1
2
25
Adele
Karl
1
2
15

47. Rounds
Round 1
Candidates ranked “1”
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Nakamura 30
Rosie 20
Li 25
Adele 15
WINNERS:
Nakamura
Nakamura
Karl
1
2
30
Rosie
Karl
1
2
20
Li
Adele
1
2
25
Adele
Karl
1
2
15
Nakamura had 4 votes over the Quota
His 4 votes are transferred to his
voters second choice
In our SIMPLE example all
Nakamura’s voters voted Karl second
Karl gets 4 more votes and
added to the count!

48. Rounds
Round 2
First vote transfer
EXAMPLE:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Rosie 20
Li 25
Adele 15
Karl 4
WINNERS:
Nakamura
Nakamura
Karl
1
2
4
Rosie
Karl
1
2
20
Li
Adele
1
2
25
Adele
Karl
1
2
15
Karl is added with 4 votes
Nobody meets the quota
Karl has the lowest votes as is
eliminated.
Karl is ELIMINATED

49. Quota Calculation
& Transfer Methods can
impact the final result.

50. Arguments and Counter
Arguments for STV.
Q10

51. Argument For STV
STV gives a better chance to
minority favoured candidates, and
encourages diversity.
It is more likely to smaller groups of
people to be represented in the
result.
Most popular candidates may not
gain a seat.
Popular second choice candidates
suffer.
Counter
Sec 1
Sec 2
1
2
40
Boris
Adeola
1
2
20

52. Argument For STV
STV minimises vote waste.
Votes are transferred to next
preferred candidates, ensuring a
greater chance of proportional
representation.
STV counting system is so complex
that most voters do not understand
the system.
This may cause voters to not
understand how to vote, and
therefore vote not according to their
preference.
Counter

53. Argument Against STV
In STV, you cannot vote for two or
more people equally.
The second choice candidate is at a
massive disadvantage.
Over a large amount of voters this
may not matter.
Around half will put Candidate A first
and half will put Candidate B first.
Effectively, they will cancel out.
If more people put Candidate A first,
then the voters probably prefer
Candidate A.
Counter
Boris
Adeola
1
1

54. Other Interesting
Points
Politics Specific:
- Favours large parties when only a few seats
(quota is high, so only large parties can
obtain a seat).
- Reduce role of political parties.
- Parties putting forward too many candidates
risk votes being spread too thin between
them.
Vacancies: Filling vacancies between elections is
complex
Lack of Candidates: Not enough candidates result
in winners in Round 1
First Choice Loss: First choices may not get
elected, whilst second choices can.
System: Needs software.

55. Advice
Q11

56. Your first ranked candidate
has advantage over your
other ranked candidates.
OBVIOUS ADVICE ALERT

57. Voting “intelligently” is
not advised.
HELPFUL ADVICE ALERT

58. Understand your
“bubble”.
HELPFUL ADVICE ALERT
“Everyone I spoke to” is always likely to be people from a similar
industry, native-speaking country, age and other demographics to
you.

59. Happy Voters?
Li
Rosie
1
2
35
Rosie
Adele
1
2
20
Nakamura
Karl
1
2
25
Example Election:
5 Candidates
3 AB Seats
105 Votes (5 Bad)
Quota: 26
Adele
Karl
1
2
15
WINNERS:
Li
Rosie
Nakamura
�������
WINNERS:
Li, Rosie, Nakamura

60. Thank-you!
Natasha Rooney
@thisNatasha
nrooney@gsma.com
Q1 Ireland
Q2 Malta
Q3 New Zealand
Q4 Nepal
Q5 Pakistan
Q6 India
Q7 Scotland
Q8 Canada
Q9 Stack Exchange
Q10 Cambridge University
Q11 Oscars

61. References
- Voting2016, W3C Wiki
- Single transferable vote, Wikipedia
- Droop Quota, Wikipedia
- Counting single transferable votes
- What is STV? Single Transferable Vote
Explained…, YouTube
- Politics in the Animal Kingdom: Single
Transferable Vote, YouTube
- Meek STV Explained