>Forest W Simmons wrote (March 11, 2007): > > >Another nice method, Jobst's TACC (Total Approval Chain Climbing), also >gives b as winner. > >Recall that Jobst initializes a "chain" with the lowest approval >candidate, and (moving up the approval list) adds only those candidates >to the chain that pairwise defeat each of the other candidates >currently in the chain. > > >
> From Jobst Heitzig (March 4, 2005): > > > >TACC (Total Approval Chain Climbing): >------------------------------------------------ >1. Sort the candidates by increasing total approval. > >2. Starting with an empty "chain of candidates", consider each >candidate in the above order. When the >candidate defeats all candidates already in the chain, add her at the >top of the chain. The last added >candidate wins. > > Chris Benham wrote: >TACC seems to have the curious property that if there are three >candidates in a top cycle, the most approved can't win unless it pairwise >loses to the second-most approved candidate. This doesn't seem to cause any >monotonicity problem, but it does seem to be much more vulnerable to >Burial than the other candidate methods: > >46: A>>B >44: B>>C (sincere is B or B>>A) >10: C > >A>B>C>A. Approvals: A46, B44, C10. > >TACC elects the buriers' candidate B (chain: B>C) while all our other >candidate methods (UncAOO, ASM,DMC,AWP) elect A. > > TACC having that curious property and so electing B here shows that it spectacularly fails the Definite Majority criterion. Maybe that is forgivable for a FBC method like MAMPO, but not for a Condorcet method that bases its result on nothing but pairwise and approval information. >31: A>>B >04: A>>C >32: B>>C >33: C>>A > >A>B>C>A Approvals: A35, B32, C33. > TACC makes the chain B>C and so elects B, but A is more approved than B and also pairwise beats B so this is also an example of Definite Majority failure. Chris Benham ---- election-methods mailing list - see http://electorama.com/em for list info
