On Wed, Jul 1, 2009 at 10:34 PM, Dave Ketchum<[email protected]> wrote: > Approval data - needs thought but my initial thought is as if each > approval was a plurality vote - does mean a voter approving 2 gets 2 votes > counted but relative counts per candidate comes out ok. > IRV or Range - examples of methods that should be avoided by states > willing to have their data included - unless they are willing and able to > convert to a method that is supported.
I would group them as Plurality: A vote for candidate A is considered A>(others) Condorcet: Matrix is provided directly IRV: Extract as much info as possible, for example Round 1: A: 100 B: 82 C: 41 D: 13 100: A>(others) 82: B>(others) 41: C>(others) 13: D>(others) D elliminated 4 go to A 3 go to B 5 go to C 1 untransferable Votes are now 100: A>(others) 82: B>(others) 41: C>(others) 4: D>A>(others) 3: D>B>(others) 5: D>C>(others) 1: D (so effectively D>(others) C would then be eliminated and we would get info about 2nd choices for C. One issue here is that C>D>A would not be distinguished from C>A (as both would transfer to A). Approval/Range This are somewhat different versions of the same method. There isn't any way to reverse the process back to votes. You give each candidate a plurality vote of (votes obtained)*[votes cast/total approval]. This would at least mean that the state wouldn't be over represented. If there were 1000 votes cast and the results were A: 800 B: 400 C: 300 Total 1500 Then, the results would be: A: 800/1.5 = 533 B: 400/1.5 = 267 C: 300/1.5 = 200 I you assume that voters will use the strategy of vote for their favourite of the top-2 and all they prefer to the expected winner, you could estimate the preference table. It is possible to find a matrix that matches the approval results, but there wouldn't be a unique one. For example: "Add" A's 800 approvals 800: A 200: "Add" B's 400 approvals 800 split into: 480: A 320: A+B 200 split into 120: 80: B Total 480: A 320: A+B 120: 80: B and so on. That would result in an assumption that lots of votes cast blank votes. Another option would be to find the "top-2". This could be the 2 most approved candidates, W (winner) and S (second). It is assumed that W and S voters would not approve each other to the greatest extend possible. So, the above example becomes >From the results: A: 800 B: 400 C: 300 Total 1500 A and B are top-2, if 800 approved A and 400 approved B, then at least 200 must have approved both. This assumes 600: A 200: A+B 200: B This means that every voter is assumed to approve one of the top-2. The rest of the candidates could then be assumed to be random. The full process would be 1) Assume all ballots are blank 2) Process Candidates from most to least approved 3) If any ballots are blank, then designate them as approving the current candidate 4) Distribute any remaining approval for the candidate randomly 5) Goto 2 This gets you a set of approval ballots which is consistant with the results. Also, it is likely to be reasonably accurate, based on the assumption that each voter only approves one of the top-2. It can be gamed if a party runs 2 candidates, as then every voter is considered to vote for one of their candidates. One option would be to fill blank ballots and then ballots approved by all the other candidates (bar the most approved). ---- Election-Methods mailing list - see http://electorama.com/em for list info
