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Sources of household net worth statistics

In this paper we look at the different sources of household net worth statistics, the differences and similarities between them, and the level of comparison customers can make between them.

Our focus is the micro unit-record sources – the household surveys Statistics NZ conducts – although we briefly mention the aggregate level and administrative data sources.

First we look at the key characteristics of the surveys we use, and then the differences and similarities between them, and finally what this means for comparing estimates over time.

Read this paper online, or download the PDF from 'Available files' on the right-hand side of this page. If you have problems viewing the file, see opening files and PDFs.

Net worth data sources

2001 Household Saving Survey (HSS)

HSS was the first household survey to measure household net worth in New Zealand. The HSS was a one-off stand-alone survey in 2001. The HSS provided statistics on the level, value, composition, and distribution of assets, liabilities, and net worth. It collected information from one individual or a couple within a household who were aged 18 years and over (Statistics New Zealand, 2016).

Survey of Family, Income and Employment (SoFIE)

SoFIE was a longitudinal survey that ran for eight years from 2002 to 2010, with the same respondents being revisited each year to build a picture of how their circumstances changed over time. It was designed to measure income, employment, and family dynamics.

In the second year of collection, we introduced a short module of questions about assets and liabilities. This was repeated every two years (Statistics New Zealand, 2016).

Household Economic Survey 2014/15 (HES)

HES collects information on household expenditure and income, and demographic information on individuals and households. Every three years, we collect detailed information on income and expenditure. In the intervening years, we collect information on income and housing costs. For the 2014/15 HES, we added questions on assets and liabilities (Statistics New Zealand, 2016).

Administrative sources

The Reserve Bank of New Zealand (RBNZ) produces quarterly estimates of the assets and liabilities of New Zealand's household sector in its Household Balance Sheet series. The RBNZ sources its data mostly from administrative sources, such as registered banks and other financial institutions, or from Statistics NZ’s national accounts data (Reserve Bank of New Zealand, 2016).

The data is at an aggregated level and is for the entire household sector. This means the estimates include people living in non-private dwellings – such as rest homes, hospitals, and student accommodation – and people living overseas who have assets or liabilities in New Zealand. We do not include these people in household surveys.

Key differences between the household surveys

Purpose of the survey

The three surveys were conducted for different purposes so each has a different focus for net worth.

The main and sole purpose of the HSS was to collect detailed net worth information, which was not the main purpose of the other two surveys. SoFIE’s main purpose was to measure changes in income and employment over time for a set group of people. In income years, HES’s main purpose is to provide indicators on how personal and household income, housing costs, and living standards change over time. In net worth years, HES collects information on New Zealanders’ wealth (assets and liabilities).

Level of detail we collect

The differing purposes mean that the level of information collected by the surveys varies. HSS and HES both collected detailed information while that in SoFIE was not as detailed.

There are three main differences in the level of detail between the surveys.

  • SoFIE collected less information on trusts, superannuation schemes and property, and business and farm assets than HES and HSS.
  • Minor differences exist in the way many variables were asked about, including the differing dollar limits we placed on values in all the surveys.
  • HES and SoFIE included the value of consumer durables and household goods. HSS excluded most consumer durables, except leisure and sporting equipment worth more than $1,000.

Survey populations

Although the populations that all three surveys measure (the target population) are generally the same, there are slight differences between them.

The target population for the three surveys is the usually resident population of New Zealand living in private dwellings and over a certain age. For HES and SoFIE this age is 15 years and over while for HSS it was 18 years and over.

While SoFIE is a longitudinal survey, in which we revisited the same respondents each year, it can be analysed at a point in time (or cross-sectionally) – the people living with these original respondents were also interviewed.

We created cross-sectional weights for both the original respondents and their household members, to represent the target population for each year of the survey. However, because of limitations in producing cross-sectional weights for a longitudinal survey, estimates are likely to be less accurate than estimates from a true cross-sectional survey (like HES). The limitations are because a longitudinal survey becomes less representative of the population the longer it goes on; for instance, immigrants and returning New Zealanders are less likely to be surveyed.

Unit of analysis

Who we produce statistics about also differs between the surveys.

For HSS, we selected one respondent aged 18 or over in each household. If this person was part of a couple, we interviewed the couple together as one unit. Because only one person or a couple is selected, this means we did not collect information about the assets and liabilities of the entire household. The HSS does therefore not provide estimates of household net worth.

For SoFIE, while we collected information from all members of the household where an original respondent lived, the data can only be analysed at an individual level. Our priority when creating the cross-sectional weights was individual-level weights, so we only incorporated population-level benchmarks in the weighting process and not household-level benchmarks. This means we cannot produce household estimates.

For HES, we interview all household members aged 15 and over and collect information on their assets and liabilities. This means the data can be analysed at a household or individual level.

Implications for comparisons over time

Even with the differences mentioned above, in general the estimates from the surveys are comparable over time because they collect similar information for a similar population. In practice, this means the high-level estimates (eg median net worth, median assets, or median liabilities) are comparable between surveys.

However, when looking at a more-detailed level, such as estimates for a certain asset or liability type, or for certain sub-populations (eg age groups), comparisons between the surveys are not as valid.

Customers should also remember the surveys are sample surveys, and the estimates are subject to a degree of error that can affect comparisons over time – even between different years of the same survey.

References and further reading

References

Reserve Bank of New Zealand (2016). C22 Household balance sheet. Retrieved from www.rbnz.govt.nz.

Statistics New Zealand (2015). Household Economic Survey (Income): Year ended June 2015. Retrieved from www.stats.govt.nz.

Statistics New Zealand (2016). Household Net Worth Statistics: Year ended June 2015. Retrieved from www.stats.govt.nz.

Further reading

Bascand, G, Cope, J, & Ramsay, D (2006, November). Selected issues in the measurement of New Zealand’s saving (s) (PDF, 307kB). In Reserve Bank of New Zealand Workshop on Saving (Vol. 14). Retrieved from www.stats.govt.nz.

Ramsay, D (2006). The measurement of net worth in New Zealand (PDF, 121kB), paper for the 29th General Conference of the IARIW, 2006. Retrieved from www.iariw.org.

Reserve Bank of New Zealand (2015). Improvements to household balance sheet statistics (PDF, 179kB). Retrieved from www.rbnz.govt.nz.

Published 2 August 2016

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