> Nathan Larson asked: > > Does anyone have any comments in reference to this critique > of STV as applied to choosing three pizza toppings? The issue > is whether it's fair to transfer the surplus votes from the > winners before transferring votes from the losers. >
The person who wrote the comments you quoted (below) does not understand the origins of STV-PR or understand how it is generally intended to work. Instead, the writer shows a classical social choice approach to interpreting the information on the ballot papers. But the preferences marked on an STV-PR ballot paper should not be interpreted in that way. Instead, they should be seen for what they are, contingency choices, to be brought into play ONLY in the event that the voter cannot be represented by his or her first choice candidate. STV-PR was not devised in an attempt to identify some great community-wide consensus (maximising some imputed social utility). Rather, STV-PR was devised to ensure that each significant point of view within the electorate was represented fairly (as expressed by the voters' responses to the candidates who had offered themselves for election). Originally, the intent was to maximise the diversity of representation rather than maximise the consensus of representation, but there has been some de facto shift in that by changes made to the counting rules (for the extremes, compare Dáil Éireann STV rules with Meek STV rules).. One of the undertakings normally given to voters in any STV-PR election is: "under no circumstances can a later preference harm an earlier preference". This is completely consistency with the 'contingency choice' approach to marking preferences. Any other approach would discourage voters from marking all the preferences they really have or, worse, open the door to tactical voting on a large scale. Seen from this perspective, it will be clear that it is essential to transfer any surplus before you consider the exclusion of the candidate(s) with fewest votes. Where the surplus is so small that it could not change the order of the bottom candidates, some STV counting rules provide for the transfer to be held in abeyance, but that doesn't alter the general principle. James Gilmour > --- > What you describe would indeed work, however.... > > Suppose the second choices of the 100 "winner" (pepperoni) votes were > one half for mushrooms, one half for onions. This, if I follow the > numbers correctly, means that mushrooms and onions would win (with 40 > and 56 respectively). But look: you have completely ignored the second > (and third) choices of the folks who didn't vote for pepperoni as first > place. You just disenfranchised 56 voters. Why should only the > pepperoni-first voters be the ones who get to exercise their second and > (possibly) third choices? Doesn't seem fair to me! Those 56 NAP > members who didn't vote pepperoni first may ALL have voted (yuk) > anchovies as their second choice. Clearly that would exceed the quota > and anchovies would have garnered MORE votes that any of the > non-pepperoni choices. But you trashed them. For shame! > > With smaller numbers the problems become more apparent. I am taking the > liberty of e-mailing you directly the essay I did some years ago. > Enjoy! Meanwhile I'll think about constructing a counter example where > there is no choice but an arbitrary choice (following your rules) that > causes a different outcome. > > But not tonight. Too late. > > > John > > John D. Stackpole, CPP, PRP Voice: 301.292.9479 > Parliamentary Services Fax: 301.292.9527 > 11 Battersea Ln. [EMAIL PROTECTED] > Ft. Washington, MD 20744-7203 ---- election-methods mailing list - see http://electorama.com/em for list info