A stats expert says the 2018 Census will be "woefully inadequate" when it comes to the finer data.
An independent review has criticised the handling of last year's census that led to an "unacceptably low" response rate.
Stats NZ chief Liz MacPherson has taken full responsibility and resigned.
Victoria University professor Richard Arnold told Mike Hosking there will be shortfalls, despite plugging the census with additional data.
'There will be information missing about the number of small ethnic and religious groups, along with geographical distributions, which is a real shame"
Arnold says the census is used to detect non-responses in other surveys.
"All of these social surveys, the only reason we know we are missing people is because of the census which tells us so. If that is unreliable, we have a real problem."