KEY POINTS:
The much-maligned opinion polls disagreed among themselves but the trend got remarkably close to the actual result.
The trend for the National bloc (National, Act and United Future), starting from late April and projected forward to election day, came out at 50 per cent - bang on the 50.1 per cent election-night result. The bloc's 65 seats on election night was two more than that of the poll projection.
Within that, National was overestimated by around 2 per cent, Act underestimated by nearly 1.5 per cent and United Future underestimated by about 0.5 per cent. The special votes, still to be counted, are likely to lift National's share of the vote - and it is the final result, including special votes, that the polls aim to mimic.
The late April-November trend for the Labour bloc (Labour, Greens and Progressive) overestimated the election-night out-turn by a little over 2 per cent and by two seats, 55 to 53. Within that Labour was overestimated by a little over 2 per cent and the Greens by two-thirds of a per cent and Progressive was underestimated by half a per cent.
On recent past experience, both Labour and the Greens are likely to gain from the special votes and bring their final share nearer to the poll trend projection.
The Maori Party projection was very close. New Zealand First was underestimated by about 1.25 per cent.
The Herald-DigiPoll survey got closest of the individual last pre-election polls to matching overall the scores for the two blocs. It was 0.3 per cent over for the National bloc and 1.3 per cent over for the Labour bloc, for an overall error of 1.6 per cent. Next was TV3: 1 per cent under for the right and 1.3 per cent over for the left, for an overall error of 2.3 per cent. The corresponding error rates for the rest were: TV One 0.1 per cent under and 3.3 per cent over, 3.4 per cent overall; Fairfax 4 per cent over and 2.1 per cent under, 6.1 per cent overall; Morgan 3 per cent under, 3.4 per cent over, 6.4 per cent overall.
All but Morgan overestimated National; Morgan substantially underestimated it. The record on Labour was mixed. All but DigiPoll substantially overestimated the Greens. Only Fairfax and Morgan picked the Act surge. All but Morgan underestimated New Zealand First.
