The Statistics Minister admits some data from the 2018 Census is "likely to be compromised" after it struggled with response rates.
James Shaw, the minister and co-leader of the Green Party, said on Tuesday there had been "failings" and admitted "some of the outputs are likely to be compromised".
His comments follow a damning review of the 2018 Census which highlighted how it "represented a significant change from its predecessor in 2013" and "unanticipated challenges resulted in a less than optimal outcome".
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The census had a new digital-focus, but it was revealed in June last year by Stats NZ boss Liz MacPherson that participation was lower than previous years, sparking an inquiry in October into what went wrong.
The national population response rate for the 2018 Census was 83.3 percent compared to its target of 94 percent, the review found. That compares to a response rate of 92.2 percent achieved in the 2013 Census.
The review also found that just 68.2 percent of Māori participated in the 2018 Census, down from 88.5 percent of respondents in 2013. The response rate from Pasikifa people was just 65.1 percent down from 88.3 percent.
The botched results led to MacPherson resigning on Tuesday after she conceded Stats NZ had been "too optimistic, placed too much emphasis on the online census, and did not have robust contingency plans".
The review, led by New Zealand management consultant Murray Jack and Canadian statistics expert Connie Graziadei, outlined weaknesses in "overall governance and strategic leadership".
It noted "high-level assumptions" taken by Stats NZ, including the assumption that there would be a 70 percent online take-up and that the first release of census data would be in August 2018.
More than a year later, it's been revealed the first set of results will come out in September this year, followed by more data drops over the following months.
Shaw said the new census model "was not executed according to the plan".
"My view is that Stats NZ has not been on a stable financial footing for some time, that's why our Government put $136.5 million into Stats NZ over the course of the next four years in the last Budget."
He said the response rate - the amount of people who filled out a form - was lower than anticipated. But he said adding administrative information to those responses means some the output of Stats NZ data won't be too bad.
"We had a poor response rate but a good coverage rate," Shaw said. With added administrative data, he said there will be sufficient information for use by the Electoral Commission for redrawing electoral boundaries.
However, due to the low response rate from Māori, Shaw admitted that iwi affiliation, used to understand population and for Treaty settlements, will be compromised.
Rahui Papa, spokesperson for the Data Iwi Leaders Group, said in a statement that the organisation has been liaising with Stats NZ to develop solutions to remediate some of the data gaps.
National's Statistics spokesperson Dr Jian Yang is now accusing Shaw of not being "involved in his department" and using MacPherson's resignation as a "scapegoat".
"He let things spiral out of control to the point where much of the data may no longer be useful," Dr Yang said. He labelled Shaw a "hands-off" minister.
Shaw brushed off the criticism, saying he "specifically asked reviewers to look into the role that ministers had to play, and asked if there was anything ministers could have done".
He claimed the reviewers said in an internal review that ministers are only as good as the information they're told.