Opinion: Can we trust the polls these day?

Bill English and Jacinda Ardern. Photo/file

The latest election poll had a shock in store for National, with Labour edging ahead in support.

In the One News Colmar Brunton Poll, the results of which were announced on Thursday before the leaders' debate, Labour was at 43 per cent support, ahead of National on 41 per cent.

But, as any politician will tell you, the only poll that counts is on election day.

The accuracy of modern polling has been under the spotlight in recent years, particularly after many polls failed to predict either Brexit or President Donald Trump.

Looking at the methodology gives me an inkling as to why that might be.

The intention with political polls is to survey a group of people that accurately reflects the population of the country. Any poll undertaken in New Zealand would aim to get roughly the same proportion of men, women, Pakeha, Maori, workers, retirees, business owners etcetera as the general population.

Yesterday, I did a quick Google search on the methodologies used by five of New Zealand's main political pollsters. All five relied on phone surveys. One only surveyed landlines, one targeted a mixture of landlines and mobile phones, the other three did not specify the types of phones.

It is very unusual for anyone under the age of 35 to have a landline phone unless they either live with their folks or run a business from home, and this is becoming more common in the older generations as well as mobile calling and data prices come down.

It's also common for young people to ignore a phone call from a number they don't recognise, knowing that if the call is important, the caller will leave a message.

I often wonder if the reliance on phone surveys is partly why polls seem to be less effective these days.

I guess we'll find out on September 23.