Special Vote Predictions — DCC Central Ward & STV

Over the weekend, I did some analyses of the Dunedin City Council Central Ward election, which has produced a surprising amount of interest. The latest iteration of the graph (which isn’t really all that different to the earlier) is reproduced below. Having had some days to mull over it, I’m now prepared to make some predictions on what might happen with the special votes.

Nothing — mostly, I think with only 300 votes left to count that it is unlikely that the results will change.

Butler — There has been some suggestion that with Butler only 57 votes behind Weatherall, that she might catch him on specials. I agree with Janine Hayward that this is unlikely. This is because she would need a monstrous swing in the special votes (a reasonable number of which are likely to be invalid). Secondly, and quite importantly, as the last candidate to be excluded, all other unsuccessful candidates votes have already been redistributed, so there are not likely to be any further surprised from transferring votes. UNLESS, one of the currently deemed elected councillors is excluded, in which case their later preferences might give her the edge (see my next point).

Marlow v. Stevenson — To my mind, the biggest chance of change probably hinges around the point I’ve marked with (7) on the graph. Marlow is eliminated with 54 votes less than Stevenson (who goes on to be elected). Special votes can favour more conservative candidates (although sometimes also green candidates, as we’ve just seen with the Wellington mayoralty). If Marlow was to edge out Stevenson (and Marlow does quite well on the transfer at Dixon’s elimination), then I suspect Stevenson’s vote would transfer to younger/lefter/female candidates, which I suspect would boost Hawkins and Butcher. Most likely, Hawkins would then replace Stevenson as an elected councillor. As to Marlow, his elimination favours Hudson (who at that stage is quite far behind Weatherall), so that could be change there as well. Maybe. This whole scenario is very unlikely, however.

Notes to graph:

  1. Thomson and Vandervis exceed threshold to be elected on first preferences, so their ‘surplus’ vote is redistributed proportionately to their second preferences.
  2. On the exclusion of Gallagher, MacTavish (green line) receives a strong boost
  3. Staynes (brown line), receives a steady stream of later preferences, rising strongly as other candidates are excluded.
  4. When Hawkins is eliminated, MacTavish receives a large boost from his subsequent preferences.
  5. However, because MacTavish has already been elected, these votes then bolster Butcher and Stevenson.
  6. Despite polling strongly on first preferences, Butler receives disproportionately fewer late preferences, and is the last candidate to be excluded.

Other observations

On the whole, this really shows STV in action. There are several groups of candidates, who while not formally aligned, are clearly aligned in the minds of voters. The way that Gallagher and Hawkins (two young liberal men) boost liberal women (MacTavish, Stevenson, Butcher) on elimination reflect one aspect of Dunedin. And also the way that business-oriented men (Walls, Marlow) boost other business-oriented men (Staynes, Hudson, Weatherall) show the transfer in practice again.


About James

I'm a scientist. Sometimes I get distracted.
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