Subnational Family and Household Projections

Nature of Projections

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.

Only the medium projection has been formulated to produce demographically plausible results, by assessing both observed historical trends and likely future trends. Other projections may project significantly different numbers of male and female partners in couple-without-children and/or two-parent families. Although living arrangement type rates are formulated to account for changing social patterns, there is 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 re-partnering, and dissolution
• propensity of young adults to stay in the parental home
• propensity and ability of people to live alone
• presence of other relatives (for example, extended family) and non-related individuals (for example, 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 healthcare
• 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 children, or one parent with children, usually living together in a household. A household is defined as one person usually living alone, or two or more people usually living together and sharing facilities (for example, 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.

Which projection should I use?

We have produced three alternative projections by combining three population projections with 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 living arrangement type rates(LATRs) assumes LATRs will change linearly between 2013 and 2038.

At the time of release, we consider the Medium projection the most suitable for assessing future family and household changes. Moreover, only Medium 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. The other projections allow users to assess the impact on the number of families and households resulting from different population scenarios.

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

1996

The 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.

2004

A new 'propensity' method is used to produce subnational family and household projections, superseding the 1996-base subnational 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.

11 Other