How did the polls do? (Provisional Election Night result)

This table shows the provisional election result and all the final pre-election poll results.

Table 1

This table shows deviations from the final result, for each party and poll.

Table 2

A few initial thoughts:

  1. Well done DigiPoll.
  2. Looking at these results, I see no evidence of the ‘National bias’ that some people talk about.
  3. If there is any poll bias, it appears to be toward the Green Party.
  4. The landline bias/non-coverage issue is a red herring.
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10 thoughts on “How did the polls do? (Provisional Election Night result)

  1. Thanks. There is a historical trend of the Greens support being overstated, IIRC this is the third successive election that’s happened. Any ideas why?

    1. I would assume that they have large support in the 18-24 age group, who would answer the polls but are less likely to be bothered voting on the day.

      1. You could be on to something there. Some polls do filter on ‘likelihood to vote’, but I think some people will say they are likely and still not vote.

  2. The greens do seem to more consistently be over-estimated in polls, but this might be the election specific mechanism that makes for the previously apparent over-estimation of National. Really we don’t have enough datapoints.
    BIt might be that where either left or right are perceived to be dominant, you might see movement away from the centre, and movement to the centre where a bloc are not. This is wild speculation, but it would be interesting to see whether the greens still appeared overestimated where a left bloc win was predicted.
    Whatever else, it is a massive massive win for probability sampling.

  3. Similar comparisons for previous elections? 2011, 2008, 2005? Conclusions (about bias or whatever) based on more than one realisation would provide more insight.

    Also, the final results may look different. e.g. the Greens may do a bit better in the specials.

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