[EM] PR-STV and vote management

[raphfrk at netscape.net]

  I was thinking about an easier solution to the vote management problem. 
 This is where it is sometimes in a party's interests to try to split their support
 equally between two candidate due to exhausted ballots. In effect, they 
 get a candidate elected without a quota.
 
 For example, assume a 3 seat election and 4 candidates.
 
 12500: A
 9000: B
 18500: (C1,C2)
 
 Voters might vote
 
 12500: A
 9000: B>C1>C2>A
 12000: C1>C2
 6500: C2>C1
 
 Quota is 10000 (approx)
 
 Round 1: A is elected, all his votes are exhasted
 A: 12500 *
 B: 9000
 C:1 12000
 C2: 6500
 
 Round 2: C1 is elected and votes transfer to C2
 
 A: 10000*
 B: 9000
  C1: 10000*
 C2: 8500
 
 B then wins the last seat as C2 is eliminated.
 
 However, if C1 and C2 had evenly split their 18500 votes, they would have won both 
 seats as they would have had 9250 votes each and B would have been eliminated first. 
 This causes parties to participate in 'vote management', the effect of which is that it is 
 no longer tactically correct to just rank the candidates in order of your choice.
 
 The best solution would be to re-calculate the quota after each round. However, this 
 would greatly complicate the counting process (especially if it was hand counted).
 
 However, really all that is needed is to recalculate the quota once at the end. 
 
 The rule would activate when
 a) there is no candidate with a surplus to distribute
 b) the number of uneliminated candidates is one greater than the seats to allocate
 
 The quota is recalculated and surplus transferred to one of the remaining
 2 unelected candidates.
 
 Round 3 would change to:
 
 Quota recalculated: (10000+9000+10000+8500)/4=9375
 
 A: 9375 (transfers 625 and they exhaust)
 B: 9000 (below quota)
 C1: 9375 (transfers 625 to C2)
 C2: 9125 (625 transferred in)
 
 Ideally, this should be repeated until it converges. In fact, it is probably
 relatively easy to work out mathematically what the final result would be
 without actually counting the additional rounds.
 
 Anyway, the result is that C2 has more votes than B and is thus elected. This
 eliminates the tactical benefit to voters who participate in vote management, 
 which allows them to be honest. It has the additional benefit that all elected
 candidates represent the same number of voters (at least all the ones who 
 come from the same district).
 
  Raphfrk
 --------------------
 Interesting site
 "what if anyone could modify the laws"
 
 www.wikocracy.com    
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