[EM] RCV in SF Mayoral election

Christopher Colosi colosi at gmail.com
Fri Jun 8 19:59:55 PDT 2018

They separated out ballots “exhausted by overvotes” and “under votes” from
“exhausted ballots”.  I assumed that meant there were 16,000 ballots
eliminated after all 3 choices were eliminated, but after closer analysis,
it appears you are correct that this includes voters who did not vote for 3
candidates.  However, even if only a fraction of the exhausted ballots were
fully ranked and would have ranked more, it probably still surpasses the
144 vote gap currently deciding the election.  Though then you would still
need a substantially larger number to actually sway it 144 votes.  Still,
the possibility exists.

At start
Over votes: 339
Under votes: 1,149
Exhausted: 0

At end
Over votes: 401
Under votes: 1,149
Exhausted: 16,025

So, an over vote on a second or third rank clearly didn’t invalidate the
vote until that rank was reached.  Happened 62 times on later ranks.  Only
401 such voting errors is pretty good

Undervotes didn’t change, meaning that my interpretation was wrong.

On Fri, Jun 8, 2018 at 7:21 PM Greg Dennis <greg.dennis at voterchoicema.org>

> 1. May not elect majority candidate
> I haven't done an analysis of the cast vote record, but I highly doubt
> that additional ranks would have put the winner over a majority of
> non-blank ballots. From my experience with past RCV elections, the
> exhausted ballots in the final round are largely voters who didn't use all
> the available ranks, not those who used all the ranks and saw them all
> eliminated. If a voter doesn't use all the ranks, it's an expression of
> indifference between the remaining candidates: an abstention from any round
> not including the ranked candidates. That's why including all non-blank
> ballots in the denominator when determining a "majority" is odd to me: it
> _excludes_ abstentions from the first round but _includes_ abstentions from
> the final round. My guess is you would find the winner _does_ have a
> majority if you exclude _all_ abstentions. Happy for someone to do that
> analysis.
> 2. What are your thoughts on London Breed’s response to being asked if RCV
>> is fair?
> I don't know, I'd expect most politicians to think systems that benefit
> them are "fair" and those that don't as "unfair," so I don't think this
> statement carries much of value. My $0.02.
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