A question about mouldy houses in this year's Census is part of an important social accounting exercise, says one academic.
The 2018 Census, which officially closed last night at midnight with 2.98 million people filling in forms online, included a mix of old and new questions.
The Census includes questions about mould, types of heating in homes and how people get to school or other forms of education.
Ian Pool, Emeritus Professor of the University of Waikato, said the Census should be seen as a "very important social accounting exercise".
"It is auditing the social and economic health of the country."
The nature of the questions changed from Census to Census, and there was always "intense competition" about what kind of questions that went in, he said.
In the 1871 Census there were questions about how many raupo houses there were.
Interesting changes in this year's Census include telecommunications - taking out fax, greater emphasis on internet access over landlines - and new questions relating to housing stock such as mould in homes, Pool said.
Questions on mouldy houses represent a very real need, he said.
"The chances of getting a really good national survey on mould in houses is very difficult, so I am pleased that sort of thing has been included on the state of housing stock."
Massey University sociologist Paul Spooley said the census is an interesting reflection on how society is changing, although a core purpose is to provide governments with the information that allows it to track these changes - and to make policy decisions.
Questions like how many chooks you have have long gone. The census question on religious affiliation shows a growing secularisation. The "nones" (no religion) was 42 per cent in 2013. It might be close to 45 per cent this time.
Spooley said the ethnic question will highlight the growing diversity of New Zealand, both in the variety of groups but also those who claim two or more ethnic identities. New Zealand is unusual in the way that it allows multiple ethnic self-identification in the way that it does.
He said Stats NZ carefully considers the evidence needs of Government and a more complete understanding of the state of the current housing stock is very important given the role of poor housing in health outcomes.
"The strength of the census is that it provides a picture of the whole of the country on a wide range of variables. It provides the statistical base for all the other surveys that take place. Without, we would often be guessing," Spooley said.
Census general manager Denise McGregor was delighted with nearly three million people filling in their census online, calling it a great result so far.
"We aimed for 60 per cent of those in New Zealand to complete it by midnight and we are very happy to have achieved this," McGregor said.
"It doesn't take long to complete. People are taking an average of four minutes for the dwelling form and eight minutes for the individual form."
McGregor is confident that the results from the online responses will give the best possible data.
"There has been a huge effort and we thank staff and especially the field staff and community volunteers around the country," she said.
Stats NZ has a target of 70 per cent of all Census forms being completed online by the end of the Census collection period. People can still ask for a paper form by phoning 0800 236 787.
Field teams will now start following up with households to help them complete their forms, and reminders would be sent, McGregor said.
In some parts of New Zealand, such as the Far North, Great Barrier Island, the Ureweras, and Whanganui, teams are delivering access codes and paper forms to make sure people in remote parts of New Zealand have everything they need to complete the Census over the next few days.
Meanwhile, the Census team are investigating claims by a Kerikeri couple, Rob and Jackie Gorton, that they did not receive the Census documents and a code number.
Rob Gorton said the documents had not arrived at the Quail Ridge Country Club retirement village.
He said he rang the Census contact number on Friday and Monday and told the couple could not get a code number because the documents were in the post.
"I'm annyoyed that we are spending so much as a country doing a Census and it's not accurate. It also affects funding for the area," said Rob Gorton.
A historic low turnout at the Census in Northland has been blamed for reduced population-based funding to the Northland District Health Board.
Stats NZ's online system remains open for several weeks.