joi, 20 martie 2014

Un copy-paste interesant

Recent am citit un alt text excelent, aici, despre sisteme de vot, din care reproduc, cu copy-paste mai jos. 

I remember one time when I worked for NEC Research Institute and we had to vote to decide who, among about a dozen candidates, to hire. There were several camps, each favoring a different candidate who excelled in one way or another. There were also many mediocre candidates – nonentities – whom nobody particularly wanted. Arguments grew impassioned.
So then our boss, who definitely was several watts shy of being the brightest bulb in the box, said "we have to be fair about this. Let's vote." And he right then (apparently) independently reinvented the Borda count system and told us all to provide our Borda votes (preference orderings) – by secret ballot of course, since he'd read in some managerial handbook that secret ballots were better. Then he'd add them up. There were one or two attendees who immediately objected that "strategic voting" would foul that up. My boss, of course, wasn't going to listen to a bunch of whining nerds about that.

Well, of course, since everybody there was an arrogant pushy scientist, everybody quickly figured out that the thing to do was to rank your favorite first, then artificially rank all of his perceived major rivals artificially last. Finally, by the rules of the Borda system, the non-entities had to be ranked somewhere in the middle. (Of course, you could honestly rank all the top candidates top, but that would be like having one-tenth of a strategic vote, unacceptably weak. Nobody could afford to be that stupid and ineffectual. Plus, there was no public embarrassment about submitting lies in your ballot, since everybody's ballot was secret.) Then, my boss made a great show of closing his eyes and shuffling all the ballots... then opened them and added them up... and golly... that was odd... the most-favored candidates all seemed to be ones that had been dismissed as nonentities before... they must have a good deal more support than he'd realized... hmm... the result-order really seems quite illogical and random... but after all, this clearly IS the most fair possible voting system, so we have to concede that Mr. Putz really is the truly most-favored candidate, unexpected though he may be... ok, meeting over, thanks for all your input, folks.

NEC Research Institute eventually collapsed and nearly all its scientists were fired. This particular meeting, in its small way, was one contribution to its downfall. (The parent company NEC still survives, thanks to a bailout by the Japanese government.)

AS A PICTURE: if the 3 good candidates are A,B,C then the strategic votes are:
A > nonentities > B > C (cast by about 1/3 of the voters)
C > nonentities > A > B (cast by about 1/3 of the voters)
B > nonentities > C > A (cast by about 1/3 of the voters)
total:  A,B, and C each get an average score of about N/3, whereas the nonentities get,    on average, a score of about N/2. So a nonentity always wins and the 3 good candidates  always are ranked below average. In this kind of scenario Borda actually performs worse  than plurality voting.

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