The 2023 census was the first to be designed as a hybrid between data and survey, said a Statutory Review of the census published on Tuesday in Wellington. Statistics New Zealand achieved a 99% response rate after data topped up the replies from about 4.4 million New Zealanders, or 88% of the population, the report said.

Other comparable countries are “only using administrative data to enumerate the population as a back-up to the main design of a full, traditional census,” the report said. “As a result, Stats NZ may be in a better position than many other similar statistical organisations to be moving to a full administrative-based census.”

Governments are looking to use data collected by tax authorities, the justice system and welfare agencies to augment census surveys, which become more expensive as populations increase. In New Zealand, low survey response rates, particularly among indigenous Maori, have become a headache for the statistics agency and the government, which uses the five-yearly census to plan infrastructure and social policy. 

As it gets more difficult to obtain replies, spending on the census escalates — the 2023 event cost NZ$316-million ($187-million) to produce, according to today’s report, up from NZ$126-million in 2018. 

Statistics New Zealand is in the process of developing a set of options for 2028 Census which include using administrative data first plus full enumeration for variables not found in administrative data, the report said. However, it is also undergoing significant organisational transformation that has the potential to add execution risk, it said.

As well, before moving to administrative data only, Statistics New Zealand will have to develop safe and ethical methods for the intake, use and storage of large-scale records, and will also need to gain and retain the trust of the public when it accesses administrative data, it said.

“The work Stats NZ has undertaken to date is impressive, but much remains to be done to successfully implement an administrative data-first census,” the report said. “It is also clear that whichever option is chosen will represent a major change from previous censuses and will consequently bring significant risks.”