Arrow assumes that, whether voters happen to have strict preferences or whether they instead rank some candidates equal, voters are free to report ANY transitive ranking of candidates (which might include equal rankings).
I have found no evidence, in the original work, to support this claim.
His proofs are based upon the relation 'R' takes into full account equal or distinct rankings.
While I could write to Dr. Arrow again, I would only want to do so if presented with a compelling reason based on the original work.
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