First the practical concern. Think about how an equal-ranking capability would would work on a touch-screen voting machine. I've actually designed and programmed a full-featured GUI for voting (http://ElectionMethods.org/GVI.htm), so I have thought about it a bit. My GVI does not allow equal rankings (unless you are using it for Approval). The candidates are ranked in the order they are selected (with backtrack capability, of course). How would the voter tell the machine to rank two candidates equal? The voter would have to press a button or do something to indicate that the next selection should be made equal to the previous selection. You may consider that simple enough, but let me tell you that it would be a *major* sticking point in practice. Remember all those brilliant Gore voters in 2000 who couldn't figure out how to vote for their candidate in a simple plurality election?
On the theoretical side, what exactly would an equal-ranking capability accomplish? Does it give the voter some significant strategic mechanism, or is it simply way for the voter to express indecision? If it's the latter, then it is completely unnecessary. If the voter truly rates the candidates as precisely equal down to the tenth decimal place, then it really shouldn't matter to him which he ranks above the other. If the decision is really that difficult, he can flip a coin. Why make the system more complicated than it needs to be?
--Russ ---- Election-methods mailing list - see http://electorama.com/em for list info
