3236.0 - Household and Family Projections, Australia, 2011 to 2036 Quality Declaration 
ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 19/03/2015   
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ASSUMPTIONS AND PROJECTION METHOD

Assumptions for these projections are based on changes in the propensity (proportion) of people to be in particular living arrangements. These propensities are taken from the Census of population and housing (Census). The three series (outline in table 2.1) represent a low, medium and high rate of change in the propensities. The rates of change are based on trends observed over the past four Censuses (1996, 2001, 2006 and 2011).

These assumptions are intended to illustrate a range of possible future outcomes, although there is no certainty that any particular outcome will be realised, or that future outcomes will necessarily fall within these ranges.

2.1 Projection series, Assumptions used
Series I No change in propensities. Living arrangement propensities for 2011 remain constant to 2036.
Series II Low rate of change in propensities. The rate of change in propensities from 1996 to 2011 continues at the full rate of change to 2016, half the rate change to 2021, one-quarter the rate of change to 2026, and then remains constant to 2036.
Series III Continuation of 1996 to 2011 rate of change in propensities. The full rate of change from 1996 to 2011 continues to 2036.

Before projecting the propensities out to 2036, living arrangement propensities for 2011 were 'reconciled', meaning that those living arrangements that conceptually define a household (for example, number of people who were living as a partner in a couple family with or without children, lone parents, persons living alone) are adjusted so that the number of households derived from living arrangements is consistent with the household estimates derived from Census counts. The method of calculating 'reconciled' 2011 propensities is described in paragraphs 36 to 38 of the Explanatory Notes.

Assumed rates of change, as described in Table 2.1, were applied to the reconciled 2011 propensities, by age group and living arrangement type, to give projected propensities for the period 2012 to 2036. The projected propensities were then applied to the Series B population projection (Population Projections, Australia, 2012 (base) to 2101 (cat. no. 3222.0)) to obtain projected numbers of people by living arrangement. (see paragraphs 17 to 21 of the Explanatory Notes).


Graph 2.2 illustrates this method using hypothetical data.

Graph: 2.2 Projection Method

While the use of different projected populations would also result in different numbers of households and families, in this release only one population projection series is reported. The choice of one population projection ensures that differences in projected numbers of households, families and living arrangements reflect changes in living arrangements and hence household and family structure, rather than a combination of changes in the size and structure of the future population. The effect of different projected populations on future numbers of households and families is explored in Section 9 - What If . . ..

Propensities were projected independently for Australia, each state and territory and each capital city and balance of state. To ensure consistency in the projected number of people, families and households, factors were applied to person-level data to ensure that the sum of the capital city/balance of state data, and state/territory data, add to Australia (see paragraphs 42 to 44 of the Explanatory Notes).

Numbers of households and families are then derived from the projected living arrangements of the population.