[EM] Ranked Pairs

Michael Ossipoff email9648742 at gmail.com
Sat Sep 16 21:42:27 PDT 2023

Is that RP(wv), or RP(margins) ?

RP(wv) would thwart & deter offensive strategy, an important property in
public elections.

…&, actually, it seems to me that MinMax(wv) would do that better.

That’s because, choosing only from the Smith Set RP, limits it’s choice to
the strategic top-cycle that created by the offensive strategists.

Suppose that the CW’s preferrers don’t do defensive truncation (never rank
anyone you wouldn’t approve in Approval, or whose preferrers you regard as
likely to offensively order-reverse) ?

Knowing that RP will limit its choice to their small  strategic top-cycle,
it would be easier for the strategists to be fairly sur that their
candidate would win in that top-cycle.

But, with MinMax, the winner is chosen more broadly, & could be anywhere in
the candidate-set.  …making it more difficult & risky to confidently do
offensive order/reversal.

RP(margins) might the best choice for a completely honest electorate, but
MinMax(wv) seems better for public elections, due to its better thwarting &
deterrence of offensive strategy.

Yes, MinMax doesn’t meet the luxury cosmetic look-good criteria that RP

But for one thing, I remind you that natural ( sincere) top-cycles are

So do you want to have less strategy-protection, in order for the result to
maybe look better in a vanishingly rare natural top/cycle?

…& how bad is a violation of Condorcet-Loser anyway.  “Beaten by all the
other alternatives” sounds like some kind of unanimity, but of course it
isn’t. It isn’t like a Pareto-violation. I remind you that the MinMax
winner has fewer voters preferring some particular candidate over him than
anyone else does.

Clone-Criterion violation? How bad that really in MinMax, especially when
we’re talking about a vanishingly rare natural top-cycle?

RP(margins) for a completely honest electorate.

MinMax(wv) for public elections.

..& about a primary to reduce the candidates to 5: Forget the primary. If
you think people will have trouble rank-ordering lots of candidates, I
remind you that, to vote among them in a primary, they’d still have to
examine & choose among the initial many candidates.

…harder than ranking only the ones you know & regard as deserving &
definitely in your accepts& preferred set.

On Wed, Sep 13, 2023 at 00:18 Colin Champion <colin.champion at routemaster.app>

> I notice that RP is the only election method mentioned by name in the
> Virginia agenda.
> A while ago I ran some simulations on elections with truncated ballots.
> Something I noticed was that the presence of RP in the list of methods
> made the software unacceptably slow. I didn't look into the cause, but
> there's a natural explanation, which is the fact that RP is known to be
> NP-complete when it deals correctly with tied margins, i.e. by
> exhausting over all their permutations. Presumably if some candidates
> are unpopular and ballots are extensively truncated, then tied margins
> are much likelier than with complete ballots.
> I gather that practical implementations of RP choose a random
> permutation rather than exhausting. This seems to me to bring a danger.
> The presence of a few vanity candidates (truncated off almost all
> ballots) may lead to ties, and this may lead to a comfortable winner
> looking as though he owes his victory to a coin-toss. Obviously this
> undermines the legitimacy of his win.
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