AV/IRO with equal rankings

Bart Ingles bartman at netgate.net
Wed Nov 11 17:42:54 PST 1998

There was some discussion a while back about how to handle equal
rankings in IRO.  The two methods discussed were fractional votes, and
treating them as multiple whole votes.  I believe it was decided that it
wouldn't make sense for anyone to use fractional votes, while allowing
multiple votes would cause a rich party problem (and also violate the
spirit of IRO).

It seems to me that the only remaining solution would be to use these
votes conditionally, in effect creating a ranking for them at the time
they are actually used.  You could do this based on the strength of the
candidates in question, so that a vote for (A=B) would be interpreted as
A > B if A had more unconditional votes.  Note that the opposite
wouldn't make any sense, since this could allow a neutral vote to
overturn the decision of others who had definite rankings for A and B.

When all but one of the equal ranked candidates are dropped, the vote
becomes a regular vote for the remaining candidate.  For example, if B
is dropped, the vote for (A=B) is converted to an unequivocal vote for

Since an equal vote would always give highest ranking to the candidate
with the most unequivocal votes, it could never be used to prevent a
candidate from being dropped under IRO.  In practice, this makes
evaluation simple:  just ignore equally ranked votes until only one of
the candidates remains.


40 A B
25 B
11 (B=C)
24 C B

In the first round B beats C 25:24, so (B=C) is converted to (B>C).  You
now have 40A > 36B > 24C.  C is dropped.
In the second round you have 60B > 40A, so B wins.

Since the equal votes have no influence over which candidate is dropped,
you can ignore them:
In the first round ignore (C=B), so you have 40A > 25B > 24C.  C is
In the second round you have 60B > 40A, so B wins.

This seems to conform to the spirit, if not the general definition of
IRO.  It still uses only the top level of choices in a given round, but
probably makes better use of them.

Bart Ingles

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