The projections employ an innovative approach to projection of housing demand at the sub-national level. The methodology is detailed in McDonald, Kippen and Temple (2006). Here, we provide a short overview of the approach.
Individuals and households
Houses or, more precisely, dwellings, are occupied by households. Therefore, the projection of housing demand is equivalent to the projection of the number of future households. To project future households, for any given locality, we begin with the population of individuals described simultaneously by sex, single-year of age and individual household classification type (HCT). The categories of HCT that we use are shown in Definition 1. This population table is obtained from successive censuses, in this case, from the 2001 and 2006 Censuses.
Next, the population by age, sex and HCT at each census is adjusted so that it agrees with the Australian Bureau of Statistics’ Estimated Resident Population (ERP) by age and sex for the particular locality and year. The adjusted 2006 population becomes the base for the projections. Data from the two censuses, 2001 and 2006, are used to measure age and sex specific net migration rates and transitions from one HCT category to another in the intercensal period, 2001-06.
We proceed by projecting individuals forward in time by sex, age and locality using location-specific estimates of future fertility, mortality and net annual migration. In the next stage, we apply probabilities that in ageing from age x to age x+1, a person will change his or her HCT. For example, as a 26 year-old woman living at home with parents ages to age 27, we consider the chances that she will move out and live alone, move into a group household, move in with a partner with no children, move in with a partner and child, become a sole parent, or experience no change in her household circumstances. The probabilities that we use are location-specific and take account of the simultaneous effects of migration upon HCT. For example, if in ageing from 26 to 27, our young woman also moves from a country town to a large city, we consider the association that this move will have with HCT transitions for that locality. For these projections, we assume that the HCT transition probabilities by age, sex and locality remain the same throughout the projection period as they were in the period, 2001-06.
| HCT Type | Definition |
|---|---|
| 1 | Parent in a couple family with co-resident children |
| 2 | Parent in a one-parent family |
| 3 | Child (any age) in a couple family with children |
| 4 | Child (any age) in a one-parent family |
| 5 | Partner in a couple family without children |
| 6 | A person living alone |
| 7 | Any person living with a couple family or a one-parent family, other than persons included in categories HCT1 – HCT5 |
| 8 | A group household member, including households consisting of related persons where there was no couple family or sole parent family (eg. siblings living together) |
| 9 | A usual resident of a non-private dwelling. |
Having obtained projections of individuals by location, sex, age and HCT for single calendar years from 2006 to 2021, we then collapse these persons into five household types using a simple procedure as shown in Definition 2. Individuals projected to be living in non-private dwellings (NPD) remain as individuals classified by sex, age and location.
Each household is tagged with the characteristics of a ‘household reference person’. For couple families, the household reference person is the female partner. For one parent families, it is the sole parent. For lone person households, it is the lone person. For group households, the age and sex of reference persons is obtained by using the distribution of the sex and age of persons listed as Person 1 in group households at the 2006 Census.
Dwellings
The final stage in the methodology is to attribute to each projected dwelling, a dwelling type (separate house, semi-detached, flat, other) and a tenure (owner/purchaser, public rental, private rental). To do this, we assume that dwelling type and tenure behaviour remain the same as observed at the 2006 Census within cells consisting of locality by household type and by age and sex of the reference person. For example, the 2006 Census provides the distribution of female lone persons aged 72 in the Hunter region by dwelling type and tenure type. We have assumed that this distribution (preferences and behaviour) remains unchanged from 2006 to 2021.
| Household Type | HCT Category |
|---|---|
| 1. Couples with co-resident children | Number defined by HCT1 for females and subsuming all of HCT3 and part of HCT7. |
| 2. One-parent families | Number defined by HCT2 for both sexes combined and subsuming all of HCT4 and part of HCT7. |
| 3. Couples with no co-resident children | Number defined by HCT5 for females and subsuming the remainder of HCT7. |
| 4. Lone person households | Number defined by HCT6 for both sexes combined. |
| 5. Group households, including households consisting of related individuals | Number obtained by applying a region-specific factor of average size of such households to the numbers of both sexes in category HCT8. |