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3  Data

Each year, Statistics New Zealand conducts the Household Economic Survey (HES), which collects, among other things, information on household expenditure, individual income and individual benefit receipt. The interview period runs from 1 July through to 30 June each year, with people asked about income and benefit receipt during the last 12 months.[7] The linked data cover HES surveys from 2006/07 to 2014/15. Throughout our paper, we exclude children aged 14 years or less.[8]

Typically, there are about 5,500-7,000 adults per HES year, except for HES 2014/15 where there are 11,000.[9]The HES data were linked to the IDI data in early 2016, with this paper using data from the September IDI release. Of adults aged 15 years or more in the HES surveys from 2006/07 to 2014/15, 83.3% were linked to the IRD data, with a further 1.5% of people linked to the IDI spine but not the IRD data. Table 11 in Appendix D shows that this link rate is stable over time. Because we cannot compare incomes for people not linked to the IRD data and because comparisons of incomes is central to our analysis, our study focuses only on those who can be linked to the IRD data. References in this paper to the linked population refer to those linked to the IRD data.

For most of our analysis (except when analysing benefit receipt), we pool the data across all the HES years from 2006/07 to 2014/15, and we use the income data without inflation adjustment.[10]


  • [7] Often, Statistics New Zealand and others refer to 'HES’ as the triannual expenditure survey and 'HES (Income)’ as the shortened income survey in the intervening years. Since we do not (and cannot) compare expenditure data in this paper, we use 'HES’ to refer to both 'HES’ and 'HES (Income)’ surveys.
  • [8] While some children do earn income (which can be seen in the IRD data), HES does not collect income data from children.
  • [9] Details about the exact number of people in each year can be found in Appendix D.
  • [10] As a robustness check, we performed much of the comparative of the analysis in this section using only HES 2014/15, and the conclusions did not substantively differ.
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