Universality criterion

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The Universality criterion is part of the proof of Arrow's impossiblility theorem, which states that a system gives unique results for a given set of ranked ballots. This is such a basic criterion that it is satisfied by all non-random ranked systems. However, since it was defined by Kenneth Arrow before there had been theoretical analysis of rated voting systems, it does not apply to rated ballots. This is why some rated systems, such as MCA-P, can appear to violate Arrow's theorem by satisfying all of the more-interesting criteria which, along with Universality, he proved to be incompatible.