2018 Census – real data about real people
29 April 2019
There are now records for about 4.7 million people in the 2018 Census dataset, with real data about real people used to fill the gaps after fewer people took part in the census than expected, Stats NZ said today.
As a result, Stats NZ will be able to start releasing census data from 23 September 2019.
“We’ve now created a census dataset that meets Stats NZ’s quality criteria for population structure information,” Government Statistician Liz MacPherson said.
“This means Stats NZ will use 2018 Census data to update the official population estimates and projections that many organisations use for their planning.
“The census data required for calculating the number of electorates and revising electorate boundaries are robust. Our extensive testing for this particular use confirms this. I am also confident that the data needed to support the allocation of population-based funding to DHBs will be fit for this purpose.”
The first release of data will include the census usually resident population counts; the number of general and Māori electorates; and the general and the Māori electoral population counts.
“The release of data has been delayed twice because of the complex and careful work required to lift the quality of the census dataset,” Ms MacPherson said.
“There are now records for approximately 4.7 million people in the census dataset. The number of records is 1.2 percent, or 58,000 people, less than our best estimate of the population on Census Day 6 March 2018. In 2013, the official census undercount was 2.4 percent, or 103,800 people.”
Eighty-nine percent of the total number of records comes from 2018 Census forms and 11 percent comes from other government data.
“Using strict data safety and security practices, we’ve added real data about real people to the census dataset. The data are reliable government administrative records that we hold in trust on behalf of the nation. It is not guesswork.
“The team at Stats NZ has risen to the challenge and delivered a new way of confidently combining the strengths of census and administrative records to create the 2018 Census dataset.
“We are confident that we are including genuine information about people we are sure were in New Zealand on Census Day, to help us provide as complete a picture as we can. For example, data on Māori ethnicity and Māori descent is likely to be more comprehensive than what was released from the 2013 Census,” Ms MacPherson said.
Ethnicity data is used in the DHB funding model and Māori descent data is used for the electoral population counts.
However, using other government data to compensate for missing data is not a silver bullet for all the information that a census traditionally provides.
“While Stats NZ has been able to use administrative data for key variables like age, sex, ethnicity, and Māori descent, we know we can’t do this for all census topics. As a result, following rigorous evaluation, some census data may not be judged of sufficient quality for release as official statistics. We will work through the implications of this with our customers as we confirm the data quality of each topic.”
The first of these determinations relates to iwi affiliation. Stats NZ will not release official statistical counts of iwi, because of the level of missing iwi affiliation data, and the lack of alternative government data sources to fill the gaps.
“I acknowledge this is a significant loss and we are not walking away from this situation. We are working in partnership with the Data Iwi Leaders Group, Māori interest organisations, iwi, and Māori to find real and relevant solutions to Māori data needs for Aotearoa. This will include supporting other government agencies to collect and provide good quality iwi affiliation data; supporting iwi to build their data capability; and co-designing specific data initiatives,” Ms MacPherson said.
How Stats NZ created the 2018 Census dataset
The statistical methods implemented by Stats NZ build on an investment since 2012 into researching how the population census could be undertaken mainly using administrative data.
Stats NZ has matched 2018 Census forms data with a file of administrative data that provided a good approximation of the New Zealand population. This has enabled Stats NZ to add people who weren’t counted via the census forms into the census dataset.
Stats NZ has also used 2013 Census data to add information about people’s characteristics that are less likely to change over time – for example, Māori descent and birthplace.
Most of the data added to the census dataset is real data about real people. In a departure from previous censuses, Stats NZ has not added any people into the dataset using copied data (unit imputation).
Stats NZ has also used the accurate dwelling list it built for the 2018 Census to add people into the right locations where possible. The total private dwelling count in the 2018 Census is approximately 1.87 million dwellings, 0.8 percent less than the dwellings estimate for Census Day.
Stats NZ is now evaluating the quality of the more detailed information that the census can provide, such as data about housing quality, households, and smoking. Indications are that household and family information is likely to be of lower quality than in previous censuses.
Stats NZ will continue to work closely with customers to support their understanding and use of the 2018 Census dataset. Stats NZ will provide a further customer update about progress in July.
Key dates – 2019 and 2020
Early May 2019 – technical seminars held in main centres and online.
By July 2019 – findings from the independent review of the 2018 Census released.
23 September 2019 – first release of 2018 Census data.
As in previous first releases of census data, Stats NZ will release:
• census usually resident population counts
• census night population counts
• the number of general and Māori electorates
• the general and the Māori electoral population counts needed to support the electorate boundary setting process ahead of the 2020 General Election
• dwelling counts
• census totals for some topics.
Stats NZ also expects to be able to start processing prioritised customised data requests from 23 September 2019.
The External Data Quality Panel will also release a report about methodology and data quality to coincide with the first release of data.
December 2019 – Stats NZ will submit a business case for a 2023 Census.
By March 2020 – Stats NZ will release the official census undercount and response rate in the 2018 Census Post-Enumeration Survey report. We will also release the 2018-base estimated resident population and updated population estimates for the June 2019–December 2019 period.
By mid-2020 – Stats NZ will complete the release of 2018 Census products and services.
Mid-2020 onwards – demographic projections will be released progressively, starting with national population projections and then subnational projections.
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