[EM] CR style ballots for Ranked Preferences

Forest Simmons fsimmons at pcc.edu
Fri Sep 14 14:47:44 PDT 2001

On Mon, 10 Sep 2001, Roy One wrote in part:

> One (non-Condorcet) tabulation method I like is what I call Run-Off
> Approval. It (or something similar) may have been describe
> previously. I am pretty sure it is not summable. For each ballot,
> count a vote for each candidate to the left of the Big Jump.
> Eliminate all candidates who do not have a vote from a majority of
> voters. If more than one candidate is still in contention, repeat the
> process, using the biggest remaining jump on each ballot as the
> dividing line. If all candidates are eliminated, choose the plurality
> winner from the last round.

A variation on this method is to eliminate at each stage all candidates
with less than 50 percent approval based on the largest remaining jump as
the approval cutoff.  If there are several jumps of the same size, the
median of the maximal jumps would be the approval cutoff.

This would be a rough simulation of the non-instant method that asks the
voters to decide which candidates are worthy of surviving to the next
round. All candidates with more than 50% support survive one more round.

As you mentioned, neither of these methods is likely to be summable in
polynomial size summaries.


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