On Nov 10, 2009, at 5:07 AM, Kristofer Munsterhjelm wrote: > Jobst Heitzig wrote: >> Dear Warren, >> I don't seem to understand the definition: >>> A single-winner voting system "fails the NESD property" if, when every >>> honest voter >>> changes their vote to rank A top and B bottom (or B top and A bottom; >>> depends on the voter which way she goes), leaving it otherwise >>> unaltered, that always (except in very rare "exact tie" situations) >>> causes A or B to win. >> So, when all voters vote strategic (i.e. no voter is honest) and all >> leave their ballots unchanged, then by definition "every honest voter >> changes their vote to rank A top and B bottom" but of course no system >> changes the result since no ballot is changed. Hence no system fails NESD. >> What is the misunderstanding here? > > I think he means: > > Call the first group of ballots, X, consisting of ranked ballots made by > honest voters. Now take every ballot in X and, for each ballot y, if y votes > A > B, put A first and B last, or if y votes B > A, put B first and A last, > leavin the ballot otherwise unchanged. Call the modified bundle, consisting > of these modified y-ballots, X'. > > If there exists such a group of ballots X so that the method in question > gives a different victor when fed X and when fed X', and gives either A or B > as the victor for group X', then it fails the NESD property. > > In other words: if the entire electorate decides that the dangerous contest > is A vs B and so maximally buries the one they like the least, and this > strategy pays off, then it fails this property.
That's the way I read it. In other words, interpret Majority failure as a virtue. ---- Election-Methods mailing list - see http://electorama.com/em for list info
