Notes on the data: Aboriginal fertility

Aboriginal total fertility rate, 2004 to 2007

Policy context: Fertility is an important component of population change (particularly population age-structure), and low fertility has implications for a population's ability to sustain itself [1]. Fertility levels vary between areas with different socioeconomic conditions, between metropolitan and regional areas, and among the States and Territories. Differences may exist for a variety of reasons, such as culture, social norms, employment, the economy, and socioeconomic status [1].

Fertility is measured by the total fertility rate (TFR) which represents the average number of children that a woman could expect to bear during her reproductive lifetime: it is calculated from details of the age of the female population, the number of births and the age of the mother at birth. Although there are signs that the Australian TFR is stabilising at around 1.8 children per woman, this is still well below the replacement level of 2.1 children per woman. Sustained periods of fertility below the replacement level are major drivers of population ageing. Given the potential economic impacts of an ageing population, fertility is of particular interest to policy-makers.

Reference

Australian Bureau of Statistics (ABS). Year book Australia, 2008. (ABS cat. no. 1301.0). Canberra: ABS; 2008.

Notes: Data are not shown for areas recording fewer than 20 births.

Concording of data on different boundaries

Births

Births data supplied by the Australian Bureau of Statistics (ABS) were coded to Statistical Local Area (SLA) boundaries using various editions of the Australian Standard Geographical Classification (ASGC) from 2003 (births in 2004) to 2005 (births in 2006). These data were concorded to 2006 boundaries using population-based concordances at the SLA level supplied by ABS.

Population

The calculation of rates required a population consistent with the period for which the deaths data were recoded: the population decided upon was the average of the June 2004 to 2006 Indigenous population, by age and sex (five year age groups to 15-44 years) by SLA. At the time of calculation of these rates, the only data on which this population could be estimated was Usual Resident Population from the the 2001 and 2006 Population Censuses. Initially, the 2001 data were converted to 2006 SLA boundaries using a concordance (provided by ABS) at the Collection District (CD) level which allocated 2001 CDs to 2006 SLAs on a proportional basis: these proportions were applied to the 2001 Indigenous populations at the CD level.

The intercensal estimates for 2004 were determined by progressing the five-year age group cohorts both forward, from 2001, and backwards, from 2006: these two figures were averaged to provide the estimated population for each five-year age group at 2004 (for the 0-4 year age group there was only one estimate (backwards)). This exercise was undertaken separately for males and females, and repeated for 2005: the results for 2004 and 2005 for each five-year age group were then averaged to produce estimates for males and for females: the persons estimate is the sum of these.

This method takes into account both the ageing of the population and the non-demographic intercensal change in the Indigenous population between 2001 and 2006, i.e., the change that cannot be explained by demographic factors (e.g., births and deaths), such as changes overall, and at certain ages, in the propensity to identify as Aboriginal or Torres Strait Islander.

Data quality

Almost all births in Australia are registered. However, Indigenous status is not always recorded, or recorded correctly. The incompleteness of Indigenous identification (referred to as completeness of coverage) means that the number of births registered as Indigenous is an underestimate of the actual number of births which occur in the Indigenous population. It should also be noted that completeness of coverage is likely to vary between geographical areas.

Numerator: Births to Aboriginal mothers

Denominator: Aboriginal women aged 15 to 49 years

Detail of analysis: Total fertility rate per Aboriginal woman, calculated from the sum of the age-specific fertility rates per Aboriginal woman over the four years (2004 to 2007)

Source: Compiled by PHIDU based on births data supplied by ABS on behalf of State and Territory Registrars of Births for 2004 to 2007 (unpublished); and the estimated Aboriginal population, 30 June 2004 to 2006 (refer to Notes above).