National Family and Household Projections

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Abstract

National Family and Household Projections provide projected number of families and households for New Zealand, by family type and household type, based on different combinations of fertility, mortality, migration, and living arrangement assumptions. The family and household projections are derived from projections of the New Zealand population, by multiplying the population by assumed living arrangement type rates for each age-sex group. The projections of population by living arrangement type are subsequently aggregated to give projections of families (by broad family type) and households (by broad household type).

Demographic projections provide an indication of future trends in the size and composition of the population, labour force, families and households. The projections are used for community, business and government planning and policy-making in areas such as health, education, superannuation and transport. The projections are typically updated every two to three years.

Purpose

Family and household projections provide an indication of future trends in the number and composition of families and households. The projections are used by community groups, businesses and government agencies, in planning and policy-making. The projections provide information on the changing characteristics of families and households, which are used to develop social policies in areas such as health, housing and education. For example, the ageing population and increasing single person households projections can help identify likely future service needs.

The projections are neither predictions nor forecasts. They provide an indication of possible future changes in the size and composition of families and households. While the projection assumptions are formulated from an assessment of short-term and long-term demographic trends, there is no certainty that any of the assumptions will be realised.

Citation Information

Title

National Family and Household Projections

Creator

Statistics New Zealand: Population Statistics

Publisher

Statistics New Zealand

Rights

Statistics New Zealand

Coverage Information

Temporal Coverage

  • 2013 to 2038

Topical Coverage

  • Population
  • Families
  • Households
  • Family
  • Household

Other

Significant events impacting this study series

1996

Population concept for all demographic estimates, projections and indices changed from 'de facto' to 'resident'. Population estimates based on the de facto population concept (the estimated de facto population) include visitors from overseas, but made no adjustments for net census undercount or residents temporarily overseas. Population estimates based on the resident population concept (the estimated resident population) include adjustments for net census undercount and residents temporarily overseas, but exclude overseas visitors. The reference date for projections is shifted from 31 March to 30 June.

2003

A new 'propensity' method used to produce national family and household projections, superseding the 1996-base national household projections which used a 'household head' method. The new series include, for the first time, projections of families by broad family type and projections of broad household types.

Usage and limitations of the data

Nature of Projections

These projections are not predictions. They should be used as an indication of the overall trend, rather than as exact forecasts. We update the projections every 2–3 years to maintain their relevance and usefulness, by incorporating new information about demographic trends and developments in methods.

Demographic projections are designed to meet both short-term and long-term planning needs, but are not designed to be exact forecasts or to project specific annual variation. We based these projections on assumptions about future fertility, mortality, migration, and living arrangement type patterns of the population. Although the assumptions are carefully formulated to represent future trends, they are subject to uncertainty. Therefore, the projections should be used as guidelines and an indication of the overall trend, rather than as exact forecasts.

The projections do not take into account non-demographic factors (for example, war, catastrophes, or major government and business decisions) that may invalidate the projections. Demographic trends are monitored regularly and, when it is necessary, we revise projections to reflect new trends and to maintain their relevance and usefulness.

Demographic projections should not be confused with economic forecasts. Changes in the number of people, families and households do not necessarily relate to the social and economic well-being of an area. The number of people, families and households may change independently of local economic factors.

Family and household projections

Household numbers should not be confused with building activity or dwelling numbers. 'Households' refer to private dwellings that are usually occupied by a person or group of people. Households therefore exclude non-private dwellings, unoccupied dwellings, and dwellings which are not the usual residence of people (eg holiday homes, second homes).

Projections of families and households are also affected by the uncertainty about how different social patterns will interrelate and vary by age-sex and/or birth cohort. Relevant social patterns include changes in:

  • age of cohabitation and/or marriage
  • fertility rates, timing of childbearing, and average family size
  • morbidity and mortality rates
  • rates of partnership formation, including repartnering, and dissolution
  • propensity of young adults to stay in the parental home
  • propensity and ability of people to live alone
  • propensity of older people to live in aged-care facilities
  • presence of other relatives (eg extended family) and non-related individuals (eg boarders) in a household
  • study, work, and shared-care arrangements where people are associated with more than one household
  • geographic location and mobility of the population
  • external migration patterns, including students from overseas
  • affordability of tertiary education, housing, and health care
  • ethnic mix of the New Zealand population.

Family and household concepts

These projections are based on the definitions of family and household used in the 2013 Census of Population and Dwellings. A family is defined as a couple, with or without child(ren), or one parent with child(ren), usually living together in a household. It excludes related people, such as siblings, who are not in a couple or parent-child relationship. A household is defined as either one person usually living alone, or two or more people usually living together and sharing facilities (eg eating facilities, cooking facilities, bathroom and toilet facilities, a living area), in a private dwelling. No information is available from the census on families and households extending beyond a single dwelling, or on families defined using different concepts (for example, whanau), and minimal information is available on families in non-private dwellings.

In these family and household projections, all people are allocated to one of 11 living arrangement types. The living arrangement type refers to the usual family and household role of a person based on a combination of individual, family, household and dwelling information from the census. The projections are based on allocating people to one role from several broad roles they may have within each social structure. These roles vary by age and sex, and are assumed to change over time with changes in social patterns.

The projections do not give a complete picture of the complexity of family and household structures, because people can and do have more than one living arrangement type role in any one entity, and families and households are not necessarily synonymous. Although people can have more than one residence, their living arrangement type role is generally based on the family and household structure of where they usually live, as self-identified by them in the census. Because households are defined as discrete units, the fluidity of living arrangements where people are associated with more than one household for study, work or shared-care purposes is not addressed.

Opposite-sex and same-sex couples are not projected separately, but are included in projections of 'couple without children' and 'two-parent' families.

It is also important to note that the definitions of parents and children are social, not biological. For example, parents include people aged 15 years or over usually living with at least one of their natural, step-, adopted or foster children (who is not usually living with a partner or child of their own). Similarly, a child is a person of any age usually living with one or two natural, step- or adopted parents (but not usually living with a partner or child of their own). No information is available on the strength of identified parent-child relationships in terms of emotional and/or financial support.

Base population

These projections have as a base the estimated resident population (ERP) of New Zealand at 30 June 2013. We derived this population (4.442 million) from the census usually resident population count at 5 March 2013 (4.242 million), with adjustments for:

  • net census undercount (+104,000)
  • residents temporarily overseas on census night (+82,000)
  • births, deaths, and net migration between census night and 30 June 2013 (+9,000)
  • reconciliation with demographic estimates at ages 0–9 years (+5,000).

For more information about the base population, refer to Population Estimates.

We derived the estimated number of families and households indirectly from the estimated resident population and the estimated living arrangement type rates for each age-sex group. The estimated number of families (1.247 million) and households (1.648 million) are equivalent to the census family count (1.136 million) and census household count (1.550 million), respectively, at 5 March 2013, with adjustments for:

  • net census undercount
  • families and households temporarily overseas on census night
  • change between census night (5 March 2013) and 30 June 2013
  • families and households temporarily absent from their usual residence but elsewhere in New Zealand on census night.

Method

We used the 'cohort component' method to derive the population projections. Using this method, the base population is projected forward by calculating the effect of deaths and migration within each age-sex group (or cohort) according to the specified mortality and migration assumptions. New birth cohorts are added to the population by applying the specified fertility assumptions to the female population of childbearing age.

We then used the propensity method to derive the family and household projections. In this method, living arrangement type rates (or propensities) are applied to population projections to give projections of the population in different living arrangement types. These projections are subsequently aggregated to give projections of families (by broad family type) and households (by broad household type).

The number of couple-without-children families = (male partners in couple-without-children families + female partners in couple-without-children families) ÷ 2.

The number of two-parent families = (male partners/parents in two-parent families + female partners/parents in two-parent families) ÷ 2.

The number of one-parent families = male parents in one-parent families + female parents in one-parent families.

The number of family households = number of families ÷ average number of families per family household.

The number of one-person households = number of people in one-person households.

The number of other multi-person households = number of people in other multi-person households ÷ average number of people per other multi-person household.

Alternative series

We have produced six alternative projections by combining three population projections with two variants of living arrangement type rates.

The three population projections are: Low which assumes low fertility, high mortality, and low migration Medium which assumes medium fertility, medium mortality, and medium migration High which assumes high fertility, low mortality, and high migration.

The two living arrangement type rates are: A which assumes LATRs will remain constant at 2013 levels B which assumes LATRs will change linearly between 2013 and 2038.

Each family and household projection series is denoted by the population projection and variant of living arrangement type rates. For example, series Medium B denotes that variant 'B' living arrangement type rates have been applied to the medium population projection.

At the time of release, we consider the Medium B projection the most suitable for assessing future family and household changes. Moreover, only Medium B has been formulated to produce demographically plausible results, by assessing both observed trends between 1986 and 2013 and likely future trends to 2038. Other projections may project significantly different numbers of male and female partners in couple-without-children and/or two-parent families, because the living arrangement type rate A variants are formulated solely from observed historical rates.

The other projections allow users to assess the impact on the number of families and households resulting from different population and/or living arrangement type scenarios. For example, Low B, Medium B, and High B can be used for assessing the effect of different population outcomes combined with variant B living arrangement type rates; and series Medium A and Medium B illustrate the effect of different living arrangement type assumptions combined with the mid-range population scenario.

Main users of the data

Statistics New Zealand, Ministry of Health, Government Planners/Local Body Planners, Ministry of Education, Consultants, Private Businesses.

Frequency

11 Other

Revision Information

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