[EM] IRV in action

[Rob Lanphier]

Very interesting.  It's a shame they didn't post the individual ballots 
in a way that a Condorcet tally could be run.  I started to work out how 
to reverse engineer the list based on the results, but unfortunately, 
once a batch of ballots gets transferred from candidate A to candidate 
B, it's impossible to know which ballots are which when candidate B's 
ballots get transferred to candidates C, D, and E.

This looks like a really strange example of an election.  The 
candidate/voter ratio was extremely high, and presumably, the candidates 
had an opportunity to establish a somewhat personal relationship with 
all of the voters (especially the incumbent pre-reform peers, who they 
presumably worked with in the "good old days").  Thus, it's not hard to 
imagine why the rankings were so deep compared with what you might 
expect in another type of election.

It's also interesting how they chose to whittle down the number required 
to win as ballots dropped off.  There were 423 ballots, where the first 
column lists "Votes needed to be elected: 212".  However, by the time 
you reach column 42, the votes needed to be elected drops to 134.  Is 
this standard practice in IRV, or was this done to avoid the 
embarrassing situation where no candidate in the runoff receives a 
majority, even after receiving 42 rounds of ballot transfers? 

I suppose this is an interesting problem for IRV in general.  I'd always 
been under the impression that a big selling point of IRV is that the 
winner would have "a majority", even if it's from a series of 
transfers.  However, there's no guarantee that there will be a majority 
even after all of the transferring is done.  In this particular 
election, there's no knowing how many of the 115 ballots accumulated by 
Montgomery of Alamein (the runner up) in the 42nd round actually listed 
Ullswater (the winner) next (who won with 151 votes).  If less than 61 
ballots (i.e. 212 minus 151) of the 115 Montgomery of Alamein ballots 
had listed Ullswater, then there was indeed no majority winner.

Rob

James Gilmour wrote:

>For an example of a real IRV election see
>http://www.parliament.uk/
>and select the link for Hereditary Peers By-Election.
>It is a PDF file (27 KB) so you may want to "Save target as ..".
>
>There were 81 candidates, of whom 44 received one or more first preference votes.
>There were 423 valid votes.  The count went through 42 stages, right to the wire
>for the decision between the last two.  Interestingly, there were no
>non-transferable papers until the 18th stage and the number of non-transferable
>papers did not rise significantly until stage 40.
>
>Ullswater, the IRV winner, received the greatest number of first preference votes:
>86 (20%).  So he would have been the FPTP winner.  But the runner-up did not
>receive the second greatest number of first preferences - he was third and didn't
>pick up any transfers until the 25th stage.
>
>James
>
>
>
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