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Archive for the ‘NZ Electorates’ Category

There has been a bit of talk lately about tactical voting in Epsom, and the “cup of tea” between PM John Key and ACT Epsom candidate John Banks has been in the news a bit.  So what’s going on?

The short version of the story is that in New Zealand, where we elect our Parliament under MMP, a party needs to either win 5% of the nationwide popular vote (party vote) or win an electorate seat to get seats in Parliament in proportion to their party vote. The current National party government’s coalition partner, the ACT party, won’t make the 5% threshold on current polling, and so the PM is in a position where he is motivated to throw the ACT party an electorate seat, the seat of Epsom to be precise.

So what happens if ACT do win Epsom?

Total seats won by ACT party, assuming they win Epsom.

Total seats won by the ACT party, assuming ACT win Epsom.

Total seats won by National party, assuming ACT win Epsom.

Total seats won by the National party, assuming ACT win Epsom.

This is the more likely situation at the moment: ACT win 1 electorate and 2.0 +/- 0.1 (RMS) total seats in Parliament. Under this scenario the National party would win 65.4 +-/ 0.8 (RMS) seats in parliament.

And what happens if ACT don’t win Epsom, and the National party candidate (Paul Goldsmith) wins instead?

Total seats won by ACT party, assuming National win Epsom.

Total seats won by the ACT party, assuming National win Epsom.

Total seats won by the National party, assuming National win Epsom.

Total seats won by the the National party, assuming National win Epsom.

In this situation the ACT party gets no seats in Parliament, and is 2.0 +/- 0.1 seats worse off. The plus-side for National is that they win 66.5 +/- 0.8 seats, and are now 1.1 seats better off.

You can do similar calculations for the other parties.  Here’s how everybody ends up if National win Epsom, relative to how they would have been if ACT had won Epsom:

  • National: +1 electorate seat, +0.1 list seats.  Overall +1.1 seats better off.
  • Labour: +0.6 seats.
  • Green: +0.3 seats.
  • ACT: -2.0 seats.
  • Maori: +0.0 seats.
  • NZF: +0.0 seats.
  • Overhang: +0.0 seats in Parliament.
  • (NB: rounding)

For those who wonder why Labour only gets 0.6 extra seats, vs. National’s 1.1, the answer is simple: Labour is polling just over half what National is polling in terms of the party vote. Regardless, if you ignore the probability of ACT going into coalition with Labour, Labour are still better off if National win Epsom than they are if ACT win Epsom.

This raises interesting questions regarding tactical voting for those in the Epsom electorate. Assuming that ACT will not hold a balance of power after the election and choose to go in to coalition with Labour, then Labour are better off if Paul Goldsmith (National candidate for Epsom) wins the seat, and John Banks (the ACT candidate) loses. Similar logic applies for the Greens, Mana, and NZF. ACT supporters obviously want their candidate to win. For Maori, United Future and National supporters the situation is a bit more complex, and depends on who is likely to win the election.

For that, please refer to the scenario analysis graphs below:

Scenario analysis for the most recent election simulation assuming ACT win Epsom.

Scenario analysis for the most recent election simulation assuming ACT win Epsom.

Total seats won by the the National party, assuming National win Epsom.

Total seats won by the the National party, assuming National win Epsom.

Looking at the two graphs, you might not notice too much difference. The first graph shows National with a 99.98% chance of winning a majority, and a 0.02% chaince of leading a National-ACT coalition. The second shows National with a 100.00% chance of winning an absolute majority, and a 0.00% chance of leading a National-ACT coalition. Either way, New Zealand gets a National Party Prime Minster.

So if you are a National, Maori or United Future party supporter, what is your preferred result? Based on current polling it would be option #2 above: National win Epsom.

(I should here point out the difference between tactics and strategy. On this blog, “tactics” refers to the short term: doing what is necessary to get the result you want from the next election. “Strategy” refers to a more long-term positional advantage. Pollsters are not in a position to comment on whether having ACT in Parliament would be good or bad for National, Maori and United Future supporters in the long term.)

The results of this hypothetical analysis are surprisingly simple: Labour, Green, Mana and New Zealand First supporters in Epsom, and an overwhelming majority of National, Maori and United Future supporters in Epsom should vote tactically for Paul Goldsmith. The National candidate should win in a landslide.

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