Housing Affordability Measure downloads and notes of interest

This page provides the methodology report and data tables available for downloading. We also provide notes and updates to the methodology, as well as relevant disclaimers.

Excel Data Tables

This Excel spreadsheet provides tables of data nationally, for regional and territorial authorities as well as Ward level information for Auckland.

This also includes:

  • a version of the Housing Affordability Measure Rent and Buy that compares after housing cost income with the national tenth percentile equivalised income, rather than the median – this has been used to understand the relative number of households in areas who are likely to be experiencing high stress financially.
  • household income percentile figures for territorial authorities and Auckland Wards.

CSV file

This CSV provides tables of data nationally, for regional and territorial authorities as well as Ward level information for Auckland.

This file has a weight column, this is the population associated with each row, these sum to 1 for a given year. This weight allows for values to be analysed by custom areas made up from the smaller areas.

These measures are experimental and subject to change

The Housing Percentage Measure, Housing Affordability Measure Median and Tenth Percentile, and Housing Affordability Index are experimental measures that are in development. This means regular adjustments are made to the methods and how they are presented. Additionally, the data used to produce these measures is constantly being refined and improved which could also result in changes to the series over time.

Because the full back series is updated whenever a change is made, newly-released results may differ slightly from previous releases.

Users should not combine data from different releases. If you have any analysis that you want to update from a previous version, we recommend downloading the most recent tables.

Since the data from different releases are not necessarily compatible, each release has a version number:

  • The original HAM released in May 2017 was version 1.0
  • The HAM released in August 2017 was version 1.1
  • The HAM released in June 2018 was version 1.2
  • The HAM released in December 2018 was version 1.3
  • The HAM released in July 2019 is version 1.4

Methodology Report

This Report provides the technical details behind how the data for the Housing Percentage Measures, Housing Affordability Median Measures and Housing Affordability Indices are constructed.

What is national median equivalised income?

The national median equivalised income after housing costs for all households is estimated using data from the 2013 Household Economic Survey, this is then adjusted for inflation at each time point.

In dollar amounts, income after housing costs for the average one-person New Zealand household was $662 in June 2013. Adjusting this for inflation using the Reserve Bank’s Inflation Calculator brings it to $707.40 per week in December 2018. This amount is adjusted for household size. The more people that live in a household, the more income it must have left after housing costs in order to have a comparable standard of living. The following table summarises how much income after housing costs the average household has in different situations, both in weekly and annual terms:

Definition of average income after rent, by household type, December 2018

HAM Table Graphic Definition of average income after rent by household type December 2018

Data improvements

Two improvements to the HAM data are included in version 1.4:

  • StatsNZ have improved the address coding system in the IDI, this in turn has improved our ability to produce households from the address data.
  • The Ministry of Business, Innovation and Employment has completed stability testing that allows us to provide more up-to-date HAM data. 

New population filters

The IDI data used to construct HAM identifies more people than better-validated sources (such as Census) do. To remove these almost-certainly non-existent people, the IDI population is filtered before being used to construct households. In version 1.4 two new filters have been added to further improve the household income data:

  • People who appear to have left the country long-term have been excluded.
  • People who move house shortly within a month of the end of the quarter have been removed.

For more details see the Methodology Report above.

Updated method for housing costs for HAM Buy

The method used to calculate housing costs for HAM Buy has been adjusted to make housing costs scale better with household size.

In previous versions, HAM Buy calculated housing costs by looking at 1-2 bedroom dwellings in an area. This cost was then compared to equivalised household income. This method assumes that housing costs scale with household size in the same manner as general housing costs.

In HAM Buy version 1.4, three different housing costs are calculated for each area, one for 1-2 bedroom dwellings, one for 3 bedroom dwellings, and one for 4+ bedroom dwellings. Each household has a cost applied based on how many bedrooms their current home has.

As part of this method change, we discovered that HAM Buy Percent had been calculated incorrectly in previous versions of HAM. HAM Buy Percent had been calculated for each household by dividing the buy cost by household income instead of equivalised* household income. This allocated overly low housing costs to large households.

Disclaimers

The Housing Affordability Measure is an experimental series.

It is not a Tier 1 Official Statistic, nor has it been endorsed by Statistics New Zealand. It has been created for research purposes from the Integrated Data Infrastructure (IDI), managed by Statistics New Zealand.

The opinions, findings, recommendations, and conclusions expressed in this paper are those of the author(s), not Statistics NZ.

Anonymised data

Access to the anonymised data used in this study was provided by Statistics NZ in accordance with security and confidentiality provisions of the Statistics Act 1975. Only people authorised by the Statistics Act 1975 are allowed to see data about a particular person, household, business, or organisation, and the results in this work have been confidentialised to protect these groups from identification.

Careful consideration has been given to the privacy, security, and confidentiality issues associated with using administrative and survey data in the IDI.

Further detail can be found in the Privacy impact assessment for the Integrated Data Infrastructure available from StatsNZ.

Tax data

The results are based in part on tax data supplied by Inland Revenue to Statistics NZ under the Tax Administration Act 1994. This tax data must be used only for statistical purposes, and no individual information may be published or disclosed in any other form, or provided to Inland Revenue for administrative or regulatory purposes.

Any person who has had access to the unit record data has certified that they have been shown, have read, and have understood section 81 of the Tax Administration Act 1994, which relates to secrecy. Any discussion of data limitations or weaknesses is in the context of using the IDI for statistical purposes, and is not related to the data’s ability to support Inland Revenue’s core operational requirements.

*Equivalised means that this has been adjusted for the number of adults and children in the household.

Published: September 12, 2019

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