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 Yes77.3% No22.7% (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) MAJORITARIANMAJORITARIAN O Some Approval voting U prefsSerial voting Sweden* AV = IRV = STV N 1 st 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 1 st preference onlyPreferential BINARYMULTI-OPTIONAL VOTERS’ CHOICE → → DECISION-MAKING

‘DEMOCRATIC’ (?) DICTATORS

OPTIONS Voters and their preferences ijklmnp A B C D A VOTERS’ PROFILE

OPTIONS Voters and their preferences ijklmnp A B C D A VOTERS’ PROFILE

OPTIONS Voters and their preferences ijklmnp A B C D A VOTERS’ PROFILE

OPTIONS Voters and their preferences MBC Con- dor- cet ijklmnp A B C D A VOTERS’ PROFILE

Methodology Social Choice and Social Ranking Examples of use in: 1 st 2 nd 3 rd 4 th Decision-makingElections Plurality voteAD B/CB/C UK (where it is called FPP) Kenya Two-round system DA-- New Zealand (referendums) Norway (in parliament) France Côte d'Ivoire AVBA--Australia BC/MBCCBADSlovenia CondorcetCBDA- ‘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 2 nd 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 2 nd choice 1 pt). He who votes for 3 options gives his favourite 3 pts, (his 2 nd choice 2 pts and his 3 rd 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 2 nd choice 1 pt). He who votes for 3 options gives his favourite 3 pts, (his 2 nd choice 2 pts and his 3 rd choice 1 pt). She who votes for all 5 options gives her favourite 5 pts, (her 2 nd choice 4 pts, and so on).

PARTIAL VOTING IN AN MBC If you vote for: Number of options your 1 ST pref gets: 1 pt2 pts3 pts4 pts5 pts your 2 ND pref gets: 1 pt2 pts3 pts4 pts your 3 RD pref gets: 1 pt2 pts3 pts your 4 TH pref gets: 1 pt2 pts your 5 TH 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) MAJORITARIANMAJORITARIAN O Some Approval voting U prefsSerial voting Sweden* AV = IRV = STV N 1 st 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 1 st preference onlyPreferential BINARYMULTI-OPTIONAL VOTERS’ CHOICE → → DECISION-MAKING