Household Survey Rebase: 2019-2024 Data Update

Background

The Household Economic Survey (HES) is a sample survey. The sample data from the survey is weighted to represent the total New Zealand population, using expected population totals or benchmarks.

For the published HES data - years ending June 2019 to 2024 - we used benchmarks based on the estimated resident population (ERP).

The ERP for a particular year uses census information adjusted for census coverage and for births, deaths, and net migration since the most recent census (the base year). As we move further from the base census year, the level of uncertainty in our estimates is likely to increase.

It is therefore statistical best practice to update recent historical data to reflect the latest census-based population estimates, a process referred to as rebasing. Rebasing can lead to small revisions to estimates because it changes the number of individuals or households each survey respondent is treated as representing (that is, the 'weights').

The 2018 Census has been used as the base year for the ERP, for the previously published HES data (with one exception - see Household benchmarks below). Now that the 2023-base ERP is available, population estimates after 30 June 2018 have been revised.

In this rebase, we revised the HES weights from the year ended June 2019 to 2024 based on the following 2023-base benchmarks:

• children - three five-year age groups: 0‒4, 5‒9, 10‒14 years
• sex by age groups - males and females by 14 age groups: 15‒17, 18‒19, 20‒24, 25‒29, 30‒34, 35‒39, 40‒44, 45‒49, 50‒54, 55‒59, 60‒64, 65‒69, 70‒74, 75+ years
• region - 12 regions: Northland, Auckland, Waikato, Bay of Plenty, Gisborne-Hawke's Bay, Taranaki, Manawatū-Whanganui, Wellington, West Coast-Tasman-Nelson-Marlborough, Canterbury, Otago, and Southland
• Māori adults by age - two age groups for Māori: 15‒29, 30+ years.

Household benchmarks

We also benchmark on households by region and household type - 12 regions for households with two adults or without two adults, separately.

These household benchmarks lag behind the benchmarks for people. The 2023-base household benchmarks are not currently available, so these have remained on the 2018-base.

The lag in benchmark availability has caused an inconsistency in the base year used for the HES year ended June 2019, compared with the later HES surveys. The published data for the HES year ended June 2019 uses the 2013-base household benchmarks. This rebase updates them to the 2018-base, bringing them in line with the years ended June 2020 to 2024.

Population estimate changes

The rebase resulted in a downward revision of the total HES population aged 15+ for the years ended June 2019 to 2024.

For children aged 0-14 there was a slight upward revision in the population for the years ended June 2019 to 2022, followed by a downward revision in the following two years.

The Māori population aged 15+ had a small upward revision across all years ended June 2019 to 2024.

There was a larger revision in the estimates of Māori aged 15-29 compared with those aged 30+ in the year ended June 2024.

The number of households was largely unaffected by the rebase, except for the year ended June 2019. This is because the weights for the year ended June 2019 were updated from a 2013-base to the 2018-base, whereas the subsequent HES years were already making use of the 2018-base.

Enquiries

Sarah Dovey
[email protected]

ISBN 978-1-991431-28-8