An immigration expert has slammed what he sees as New Zealand's systemic failure to recognise minority ethnic and religious communities.
This comes after Statistics New Zealand revealed that one in seven failed to fully complete Census 2018.
Massey University sociologist Professor Paul Spoonley said the use of "crude categorisations" like Asian and Pasifika by authorities hid important differences and the true diversity of the nation.
Census participants were asked to list their race and ethnic origin. But those who identified with an "infrequent" or "unanticipated ethnic group" were put under a "not elsewhere classified" group.
There are about 4000 people who had been categorised either as "not elsewhere classified" Asians or Europeans.
Spoonley said Auckland is among the most ethnically diverse cities in the world for its population size of about two million.
"Vancouver and Auckland can lay claim to being the most diverse cities in the world," Spoonley said.
"In Auckland's case, that diversity has a different dimension with the presence of a large Maori population ad well as immigrants and their descendants."
The World Migration Report in 2015 identified Auckland as being more diverse than Los Angeles, London and even New York - with 39 per cent of its population born overseas.
Spoonley said it was important for New Zealanders to care about diversity recognition because "recognition and respect are at the core of inclusiveness".
"It acknowledges an important identity for communities and it is part of our commitment as a society to making sure we reflect diversity in all its forms, not just the ones we want to recognise or feel most comfortable with," he said.
"One of my frustrations is that we tend to use crude categorisations - Asian, Pasifika - and it hides the diversity of these populations."
Spoonley said this has resulted in New Zealand having many "hidden communities", including groups such as the Peranakans, Rohingya or Uighur.
"Even as we consider more specific national and ethnic communities, it can be confusing. Who is Indian? From Fiji or India. But these labels also hide important differences. We will understand that a person is Chinese but not Hakka, and then there are groups that are ignored or overlooked for political reasons such as the Uighur," he said.
"We need to have a system which makes sense to those who manage our society, and making it more complicated is challenging. But we also need to have a system which recognises those identities that are important to our citizens and residents."
According to Statistics New Zealand, data was available only for ethnic groups that had a population of at least 100 people.
In 2013, there were 2637 grouped as not elsewhere classified Europeans and 1233 as not elsewhere classified Asians.
Spoonley said failure to recognise ethnic communities could leave them feeling marginalised and ignored.
"If we are committed to diversity recognition, then it should apply to all minority religious and ethnic communities."
Statistics New Zealand chief executive Liz MacPherson last week provided the numbers of partial responses to Members of Parliament after repeatedly denying requests of a parliamentary select committee.
Spoonley said McPherson's revelation showed that the Census "failed" in what it was supposed to have achieved.
He said the gaps in the Census responses were large and would possibly make it "irrelevant" for research.
A Statistics New Zealand spokesman told the Herald more would be said on April 29, when a media release and a media conference would take place.
"But to be clear, this is not when Census data will be released," the spokesman said.
NOT ELSEWHERE CLASSIFIED KIWIS - KEY FACTS
Asians - 1233
Most likely region lived - Manawatu-Wanganui (29.1 per cent)
Median age - 27.6 years
Born overseas - 88.2 per cent
Three in four aged 15 years or over had a formal qualification
Median income $9500
Europeans - 2637
Median age - 34.8 years
Born overseas - 87.3 per cent
More than nine in 10, or 93.8 per cent had a formal education
Median income $34,500
- Source: Statistics New Zealand 2013 Census