National Family and Household Projections

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. 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 projection Medium B 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, because the living arrangement type rate A variants are formulated solely from observed historical rates. Although living arrangement type rate variant B is 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 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. 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. en-NZ