Australian Bureau of Statistics
3228.0.55.001 - Population Estimates: Concepts, Sources and Methods, 2009
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 12/06/2009
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9.16 However, the net undercount rate as reported in previous PES summary results, expresses the net undercount as a percentage of the PES estimate of the number of people who should have been counted in the Census.
9.17 Mathematically, this has traditionally been defined as:
9.18 In both cases, the PES estimate represents the weighted survey estimate of how many people
should have been counted in the Census whereas the Census count represents the number who were counted. The reason we have reported both is that the net undercount rate is referred to in the Commonwealth Electoral Act 1918.
9.19 Details of the 2006 survey are available in:
9.20 Interim population estimates as calculated using the PES are subject to adjustments based on demographic analysis ('demographic adjustments'). These demographic adjustments are explained in more detail in Appendix 1 - Demographic adjustment.
Census undercount in states/territories
9.21 As shown in Table 9.2, there is variation in the rate of undercount for the individual states and territories. New South Wales, Victoria, South Australia and the Australian Capital Territory have shown relatively small variations. In Queensland there has been a considerable and consistent increase - from 1.7% in 1996 up to 3.7% in 2006. In the Northern Territory the rate was relatively low in 1996 (2.9%) but has risen steadily to 7.6% in 2006. The Northern Territory has consistently shown the highest rate of undercount of all states and territories.
Census undercount by age and sex
9.22 As has been observed in previous censuses in Australia, as well as censuses overseas, undercount is greatest in the young adult range, from approximately 15 to 35 years. Older adults are much more likely to be enumerated than younger adults.
9.23 At all ages undercounting is greater for males than females, averaging 3.3% and 2.1% respectively in 2006. The highest rate observed in 2006 was 8.1% for males aged 25-29. The highest rate for females was 6.0% for the 20-24 year age group.
Census undercount by marital status and country of birth
9.24 The 2006 undercount rates and their standard errors for the marital status categories and for selected countries of birth are shown in Table 9.4. To a certain extent the rates reflect the age structures of the various categories. For example, the never married category, which has the highest undercount rate in the marital status classification, includes a higher proportion of people in the 15-19, 20-24 and 25-29 year age groups, for whom the rate of undercounting is higher.
9.25 Similarly, in the country of birth classification, the population of the older source (of immigrants) countries, such as England and Scotland, have older age profiles and lower undercount rates. On the other hand, immigrants born in China and India include a higher concentration in the young adult age groups.
Census undercount by Indigenous status
9.26 In 2006, the Indigenous undercount rate was significantly higher than the non-Indigenous undercount rate. For more information on Indigenous undercount see the Technical Note in Experimental Estimates of Aboriginal and Torres Strait Islander Australians, Jun 2006 (cat. no. 3238.0.55.001).
This page last updated 11 June 2009
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