The chief executive of Stats NZ has resigned following a review of New Zealand's 2018 Census which identified shortfalls in the 'digital first' approach.
The 2018 Census was digitally-focused but it was later revealed that participation was lower than previous years, sparking an inquiry in October into what went wrong.
Stats NZ CEO Liz MacPherson has conceded the official data agency had been "too optimistic, placed too much emphasis on the online census, and did not have robust contingency plans".
"Put simply, we didn't make it easy enough for everyone to take part and that will be a key focus for the next census."
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It was revealed last year that just 90 percent of New Zealanders filled out the Census in 2018, leaving a data hole some several hundred thousand people deep. It was the lowest rate of participation in five surveys.
In Stats NZ's 2018 Annual Report it was noted that full or partial responses had been collected for 90 percent of the estimated population, compared with 94.5 percent in 2013.
The review, made public on Tuesday, has highlighted how the 2018 Census "represented a significant change from its predecessor in 2013" and "unanticipated challenges resulted in a less than optimal outcome".
It's noted in the report: "In the days following the census date of 6 March it became clear that response rates were not as high as expected."
The review also criticised Stats NZ's communications subsequent to census day, saying it has "not been transparent about response rates and plans for treating gaps, and left many stakeholders frustrated".
"The 2018 Census has struggled with response rates and has yet to deliver its first outputs. These are scheduled for 23 September, 11 months later than planned."
It's noted in the report how "many have concerns about its quality".
Minister for Statistics and Green Party co-leader James Shaw told Newshub in July last year an independent review would "look to understand why that has happened and take lessons that can be applied in the future".
The review was undertaken by New Zealand management consultant Murray Jack and Canadian statistics expert Connie Graziadei. In a joint statement, they expressed disappointment over the 2018 Census.
"It's our view that weaknesses in overall governance and strategic leadership at the programme level led to a series of decisions... that when taken together ultimately compromised the achievement of the investment objectives and several important key performance indicators."
The experts have noted how the basic model used for the 2018 Census was sound. It was the implementation of it that fell short.
"The apparent lack of understanding of how the model would perform led to deviations from the planned approach."
National's statistics spokesperson Dr Jian Yang has been scathing about the 2018 Census, earlier this month slamming Stats NZ for delaying the review findings which were supposed to come out in July.
There were calls to bring the next census to 2021. But the experts in the review have recommended that the next census be held in 2023 as planned.
"It is our view that a census before 2023 is unsafe - maintaining too much risk with insufficient time to properly redesign, test and implement a plan for success."
They also recommended more meaningful engagement with iwi and Pasikifa.
MacPherson's decision to resign has been supported by the State Services Commissioner Peter Hughes who acknowledged she has "done the right thing".
Hughes said he will start the recruitment process to replace MacPherson in the coming weeks. He has asked MacPherson to stay on until Christmas.