Polling company Colmar Brunton has shifted to mix of landline and mobile calls.
The new polling methodology is designed to give a more accurate result, according to Jason Shoebridge, CEO of Colmar Brunton's parent company Kantar Insight New Zealand.
The methodology is a mix of 50 per cent landlines and 50 per cent mobile calls.
Mr Shoebridge said 20 per cent of 18 to 34-year-olds do not have a landline to call and the number is expected to increase.
"It's about future-proofing our polls."
He said this method is "a better way to go," instead of online.
"Not speaking to someone potentially gives a disconitunity in the trend."