consensual decision making by peter emerson, the de borda institute

Peter Emerson

The de Borda Institute

August 8 2013, Wood Quay Venue, Dublin @ogpconsultirl #ogpIRL

SOCIAL CHOICESand

SOCIAL RANKINGS

The de Borda Institute

www.deborda.org

DECISION-MAKING

Questions

MEDIATION open, multi-optional

POLITICS closed, majority votes

MAJORITARIANISM

The (simple or weighted) two-option majority vote is the most inaccurate measure of collective opinion ever invented

CLOSED

QUESTIONS

SEMI-OPEN

QUESTIONS

OPEN

QUESTIONS

↑All

Prefs

DECISION-MAKING Borda

BC / MBC

C AV = alternative vote

BC = Borda Count

IRV = instant run-off

MBC = modified Borda count

STV = single transferable vote

Condorcet

(Copeland)

OSome

Approval

voting

U prefs Serial voting

Sweden*

AV = IRV =

STV

N 1st

prefs

only

Weighted majority

EU, SA, UN

Consociational

NI, Belgium

2-round voting

Norway**

T Simple majority

Ireland, UK, etc.

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 → →

PARTIAL VOTING IN A 5-OPTION MBC

• He who votes for 1 option gives his favourite 1 pt.

PARTIAL VOTING IN A 5-OPTION 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 A 5-OPTION 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 A 5-OPTION MBC

If you vote for: Number of options

1 2 3 4 5

your 1ST pref gets: 1pt 2pts 3pts 4pts 5pts

your 2ND pref gets: 1pt 2pts 3pts 4pts

your 3RD pref gets: 1pt 2pts 3pts

your 4TH pref gets: 1pt 2pts

your 5TH pref gets: 1pt

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

DECISION-MAKING Borda

BC / MBC

C AV = alternative vote

BC = Borda Count

IRV = instant run-off

MBC = modified Borda count

STV = single transferable vote

Condorcet

(Copeland)

OSome

Approval

voting

U prefs Serial voting

Sweden*

AV = IRV =

STV

N 1st

prefs

only

Weighted majority

SA

Consociational

NI, Belgium

2-round voting

Norway**

T Simple majority

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 → →

OPEN →

THRESHOLD THRESHOLD THRESHOLD THRESHOLD

HIGH LOW HIGH LOW HIGH LOW HIGH LOW

↑

C

O

U

N

T

All

prefs

E L E C T O R A L S Y S T E M S QBS + top-up

AMS = additional member system

AV = (STV) = alternative vote FPP = first-past-the-post

MBC = modified Borda count MMP = multi-member proportional

QBS

BC/MBC

Condorcet

lots

some

prefs

few

QBS =quota Borda system

S(N)TV = single (non-) transferable vote

PR-List

Swiss

PR-STV

Ireland

N Ireland

Approval Voting

AV

Australia

PR-List

Belgium

2-round

France

Bosnia ’90

Mixed FPP + PR

Croatia ’92-’95 MMP – Germany, NZ

1st

prefs

FPP

UK

Kenya

PR-list

closed

Israel, Iraq

Bosnia ’96

Kosovo*

AMS

FPP

LebanonSNTV

Afghan-

istan

PR-list

Holland

Bosnia ’00

* with set-

aside.

1 party only 1 candidate

of 1 party

1 or some candidates of

1 or some parties

1, some or all

candidates of any or all

parties

V O T E R S ' C H O I C E →