THE INADEQUATE STUDY OF SOCIAL CHOICE THEORY AND ITS WORLD-WIDE CONSEQUENCES 欢迎 Peter Emerson...
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Transcript of THE INADEQUATE STUDY OF SOCIAL CHOICE THEORY AND ITS WORLD-WIDE CONSEQUENCES 欢迎 Peter Emerson...
THE INADEQUATE STUDY OF SOCIAL CHOICE THEORY
AND ITS WORLD-WIDE CONSEQUENCES
欢迎
Peter Emerson
The de Borda Institute
德博达研究所
ZIMBABWE
President Mugabe:
Elections: first-past-the-post
Governance: majority vote
EGYPT
Constitutional Referendum
Yes 77.3%
No 22.7%
(41% turnout)
MAJORITARIANISM(majority rule by majority vote)
The (simple or weighted) majority vote is the most inaccurate measure of collective opinion ever invented.
CLOSED
QUESTIONS
SEMI-OPEN
QUESTIONS
OPEN
QUESTIONS
↑All
prefs
Borda
BC / MBC
non
Major-
C AV = alternative vote
BC = Borda Count
IRV = instant run-off
MBC = modified Borda count
STV = single transferable vote
Condorcet
(Copeland)
M
A
J
O
R
I
T
A
R
I
A
N
OSome
Approval
voting
U prefs Serial voting
Sweden*
AV = IRV = STV
N 1st
prefs
only
Weighted majority
SA, UN
Consociational
NI, Belgium
2-round voting
Norway**
T Simple majority
Ireland, UK
Twin Majority
Switzerland
Plurality
New Zealand
* a series of majority votes
** a first-round plurality and then a majority vote
1 of 2
options
1 of some options
1 or some of some options
1or some or all of all options
1st preference only Preferential
BINARY MULTI-OPTIONAL
VOTERS’ CHOICE → →
DECISION-MAKING
‘DEMOCRATIC’ (?) DICTATORS
OPTIONSVoters and their preferences
i j k l m n p
A 1 1 1 4 4 4 4B 2 3 3 1 2 3 3C 3 2 2 2 1 2 2D 4 4 4 3 3 1 1
A VOTERS’ PROFILE
OPTIONSVoters and their preferences
i j k l m n p
A 1 1 1 4 4 4 4B 2 3 3 1 2 3 3C 3 2 2 2 1 2 2D 4 4 4 3 3 1 1
A VOTERS’ PROFILE
OPTIONSVoters and their preferences
i j k l m n p
A 1 1 1 4 4 4 4B 2 3 3 1 2 3 3C 3 2 2 2 1 2 2D 4 4 4 3 3 1 1
A VOTERS’ PROFILE
OPTIONSVoters and their preferences
MBCCon-dor-cet
i j k l m n p
A 1 1 1 4 4 4 4 16 0B 2 3 3 1 2 3 3 18 2C 3 2 2 2 1 2 2 21 3D 4 4 4 3 3 1 1 15 1
A VOTERS’ PROFILE
MethodologySocial Choice
and Social Ranking
Examples of use in:
1st 2nd 3rd 4th Decision-making Elections
Plurality vote A D B/C
UK (where it is called FPP)
KenyaTwo-round system
D A - - New Zealand (referendums)
Norway (in parliament)
FranceCôte d'Ivoire
AV B A - - AustraliaBC/MBC C B A D SloveniaCondorcet C B D A -
‘DEMOCRATIC’ RESULTS
PARTIAL VOTING IN AN MBC
He who votes for 1 option gives his favourite 1 pt.
PARTIAL VOTING IN AN MBC
He who votes for 1 option gives his favourite 1 pt.
She who votes for 2 options gives her favourite 2 pts (and her 2nd choice 1 pt).
PARTIAL VOTING IN AN MBC
He who votes for 1 option gives his favourite 1 pt.
She who votes for 2 options gives her favourite 2 pts (and her 2nd choice 1 pt).
He who votes for 3 options gives his favourite 3 pts, (his 2nd choice 2 pts and his 3rd choice 1 pt).
PARTIAL VOTING IN AN MBC
He who votes for 1 option gives his favourite 1 pt.
She who votes for 2 options gives her favourite 2 pts (and her 2nd choice 1 pt).
He who votes for 3 options gives his favourite 3 pts, (his 2nd choice 2 pts and his 3rd choice 1 pt).
She who votes for all 5 options gives her favourite 5 pts, (her 2nd choice 4 pts, and so on).
PARTIAL VOTING IN AN MBC
If you vote for:
Number of options
1 2 3 4 5
your 1ST pref gets: 1 pt 2 pts 3 pts 4 pts 5 pts
your 2ND pref gets: 1 pt 2 pts 3 pts 4 pts
your 3RD pref gets: 1 pt 2 pts 3 pts
your 4TH pref gets: 1 pt 2 pts
your 5TH pref gets: 1 pt
BORDA COUNT (BC)
A full vote = n, n-1 … 2, 1
MODIFIED BORDA COUNT (MBC)
A full vote = n, n-1 … 2, 1
A partial vote = m, m-1 … 2, 1
CLOSED
QUESTIONS
SEMI-OPEN
QUESTIONS
OPEN
QUESTIONS
↑All
prefs
Borda
BC / MBC
non
Major-
C AV = alternative vote
BC = Borda Count
IRV = instant run-off
MBC = modified Borda count
STV = single transferable vote
Condorcet
(Copeland)
M
A
J
O
R
I
T
A
R
I
A
N
OSome
Approval
voting
U prefs Serial voting
Sweden*
AV = IRV = STV
N 1st
prefs
only
Weighted majority
SA, UN
Consociational
NI, Belgium
2-round voting
Norway**
T Simple majority
Ireland, UK
Twin Majority
Switzerland
Plurality
New Zealand
* a series of majority votes
** a first-round plurality and then a majority vote
1 of 2
options
1 of some options
1 or some of some options
1or some or all of all options
1st preference only Preferential
BINARY MULTI-OPTIONAL
VOTERS’ CHOICE → →
DECISION-MAKING