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New Zealand Income Survey population rebase: June quarters 1997 to 2014

We have revised estimates for the New Zealand Income Survey (NZIS), using information from the 2013 Census. We outline the changes between the originally published and revised estimates, and the introduction of regional population benchmarks to help improve the quality of our income estimates by region.

Background on the population rebase

The New Zealand Income Survey (NZIS) is a sample survey. We use statistical weights to calculate survey estimates that reflect the size of the national population. Following each census, we revise these weights so our estimates of the population can represent the latest population counts from the census. This process is called a population rebase.

Regional population benchmarks introduced

The regional population benchmarks are designed to improve the quality and the time series consistency of income estimates by region. Normally, we revise all estimates back to the previous census. However, due to this introduction of regional benchmarks, we revised the NZIS data back to the start of the series (June 1997 quarter). 

Minor changes to income estimates

This rebase had an overall downward revision in the number of working-age population and number of people employed. See Household Labour Force Survey population rebase from 2013 Census: Includes regional benchmarks to find out how the rebase affected our labour force estimates. However, there were minor changes to income estimates for each year back to 1997. In this release, we focused on changes in the June 2014 quarter to show the impacts of this rebase on the most recent data.

Table 1 summarises the changes in the key measures between originally published and revised estimates for the June 2014 quarter. Most of the changes are within 0.3 percent. The biggest change is median weekly income from all sources for all people, down 0.7 percent from the original published figure. However, this change is not statistically significant.

Table 1
Originally published and revised key measures

June 2014 quarter

 Income measure

Original
published

Revised Percent
change 
Median weekly income from all sources for all people  $600  $596  -0.7%
Average weekly income from all sources for all people  $780  $779  -0.1%
Median weekly income from wages and salaries for those receiving income from this source  $863  $863   0.0%
Average weekly income from wages and salaries for those receiving income from this source  $991  $993   0.2%
Median weekly income from government transfers for those receiving income from this source  $303  $303   0.0%
Average weekly income from government transfers for those receiving income from this source  $290  $291   0.2%
Median hourly earnings for those receiving income from wages and salaries  $21.94  $22.00   0.3%
Average hourly earnings for those receiving income from wages and salaries  $26.78  $26.87   0.4%

The graph shows that the rebased series follows the same trend as the original series back to 1997.

 Graph, median weekly income from all sources for all people

The introduction of regional benchmarks and the population rebase have a small effect on regional estimates of income. For all years within all regions, the revisions are no more than 1.3 percent (and the vast majority of changes are within 0.5 percent) for estimates of:

  • average weekly income from all sources for all people
  • median weekly income from paid employment for those receiving this source of income.

Table 2 outlines the changes between the originally published and revised estimates by region for the June 2014 quarter.

Table 2
Revised estimates and changes from the originally published estimates
June 2014 quarter

Region  Average weekly income from all sources for all people Median weekly income from paid employment for those receiving income from this source
Original published Revised          Percent change       Original published Revised Percent change
Northland  $664  $660   -0.6%  $800  $798  -0.3%
Auckland  $805  $806   0.1%  $900  $901   0.2%
Waikato  $718  $720   0.3%  $800  $800   0.0%
Bay of Plenty  $701  $703   0.3%  $788  $798   1.3%
Gisborne/Hawke’s Bay  $661  $658  -0.4%  $767  $767   0.0%
Taranaki  $797  $795  -0.3%  $885  $880  -0.6%
Manawatu-Wanganui  $646  $645  -0.2%  $744  $738  -0.8%
Wellington  $901  $901   0.0%  $959  $959   0.0%
Tasman/Nelson/Marlborough/West Coast  $733  $733   0.0%  $767  $760  -0.9%
Canterbury  $808  $807   0.0%  $829  $825  -0.5%
Otago  $799  $797  -0.3%  $815  $806  -1.2%
Southland  $808  $808  -0.1%  $840  $840    0.0%

See NZ.Stat for updated income tables: 1998 to 2014.

Updated information release tables for the entire time series are available on request.

Next release

New Zealand Income Survey: June 2015 quarter will be released on 2 October 2015 using the updated weights from this rebase.

Published 31 August 2015

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