CENSUS ESTIMATES

Census year population estimates

2.7 Census year population estimates are calculated for each state and territory by sex and single year of age (from 0 years to 115 years and over).

2.8 There are four steps involved in arriving at these estimates, the results of which are detailed in Table 2.1:

Step 1

2.9 Census counts of residents are compiled for each state and territory by single year of age and sex ('counts of residents' means that people counted in the Census who usually reside overseas are excluded, such as visiting tourists). The question in the 2006 Census from which these data were derived is as follows:

Where does the person usually live?

• For persons who usually live in another country and who are visiting Australia for less than one year, mark 'Other country'.
• For other persons, 'usually live' means that address at which the person has lived or intends to live for a total of six months or more in 2006.
• For persons who now have no usual address, write 'NONE' in the 'Suburb/Locality' box.
• For boarders at boarding school, write the address of the boarding school or college.

Step 2

2.10 The Census counts of residents are then adjusted upwards to compensate for Census net undercount. In 2006, about 3.0% of the population were not counted by the Census, while 0.3% were counted more than once. These two figures produced a net undercount rate of 2.7%. The precise degree of adjustment is based on estimates of undercount from the Census Post Enumeration Survey (PES) and to a lesser degree comparisons between Census results and independent 'demographic' and other estimates of the population - see Appendix 1 - Demographic adjustment.

2.11 The PES is a sample survey conducted shortly after the Census to estimate the number of people (and their characteristics) who did not complete or were not included on a Census form. It also detects instances of multiple counting of individuals but the number of such cases is far outweighed by the number of people who are not counted. The net undercount is therefore the excess of the undercount (people not counted) over the number of instances of multiple counting.

2.12 Net undercount for each category (i.e. state, SLA, sex, age, Indigenous status) is the net result of the PES estimate of gross undercount, gross overcount, differences in classification between the PES and Census (eg. age, sex, Indigenous status) and imputation error in the Census. Details of the 2006 PES are available in:

• Census of Population and Housing - Undercount, 2006 (cat. no. 2940.0)
• Census of Population and Housing - Details of Undercount, Aug 2006 (cat. no. 2940.0)
• Information Paper: Measuring Net Undercount in the 2006 Population Census, 2007 (cat. no. 2940.0.55.001)
• Research Paper: An Estimating Equation Approach to Census Coverage Adjustment (cat. no. 1351.0.55.019).

2.13 The 'demographic' estimates are an annual population series for Australia as a whole, compiled solely from registered births and deaths and overseas migration data from 1925 onwards (i.e. they are compiled irrespective of Census counts, see Appendix 1 - Demographic adjustment).

2.14 A detailed description of the 2006 adjustment for net undercount is contained in Chapter 9 - Data sources.

Step 3

2.15 Estimates of the number of Australian residents temporarily overseas on Census Night (RTOs) are obtained from passenger card statistics for those Australian residents returning in the twelve month period subsequent to the Census date who were overseas on Census Night. The residency status is calculated using the improved net overseas migration (NOM) method (see Chapter 6 - Estimating net overseas migration), and the residents are added to the adjusted Census counts derived in Step 2 to give Census year population estimates. The population estimates are then converted from age to financial year of birth, which for the 8 August 2006 Census date required adjusting all cohorts for the 39 day period back to 30 June by taking 39/365 of each cohort and adding it to the next one.

Step 4

2.16 As the Census does not fall on 30 June, a further adjustment is necessary to arrive at estimates for that date. For example, the 2006 Census was held on 8 August, and after Steps 1 to 3, the population estimates at 8 August were back-dated to 30 June. This used data from birth and death registrations, overseas arrivals and departures data and estimates of interstate migration for the period 1 July to 8 August.

2.1 Adjustment components of estimated resident population, Final - 30 June 2006
			NSW	Vic.	Qld	SA	WA	Tas.	NT	ACT	Aust.(a)
			'000	'000	'000	'000	'000	'000	'000	'000	'000
Persons
	Components as at 8 August 2006:
		Census count, actual location	6 585.7	4 915.3	4 046.9	1 509.0	1 986.2	470.8	217.1	327.9	20 061.6
		plus - Residents absent interstate	74.8	87.7	38.1	28.4	19.2	13.0	4.5	10.5	276.3
		less - Interstate visitors	54.3	36.2	107.5	13.8	25.1	5.5	22.1	11.4	276.3
		less - Overseas visitors	57.0	34.4	72.9	9.2	21.3	1.8	6.7	2.9	206.4
	equals - Census count, place of usual residence		6 549.2	4 932.4	3 904.5	1 514.3	1 959.1	476.5	192.9	324.0	19 855.3
		plus - Allowance for under-enumeration	157.6	113.6	148.4	36.3	64.2	9.5	15.9	4.0	549.6
		plus - Demographic adjustment	-5.1	-3.4	-2.8	-1.0	-1.3	-0.3	-0.2	-0.2	-14.3
		plus - Residents temporarily overseas	124.3	94.6	50.5	20.2	42.5	4.6	2.5	6.8	346.0
	equals - ERP as at 8 August 2006		6 826.0	5 137.3	4 100.6	1 569.8	2 064.4	490.3	211.1	334.7	20 736.6
	Backdating components to 30 June 2006:
		less - Births	9.6	7.1	6.0	2.0	2.9	0.7	0.4	0.5	29.3
		plus - Deaths	5.4	3.9	2.9	1.4	1.3	0.4	0.1	0.2	15.6
		less - Net interstate migration	-2.4	-0.1	2.4	-0.2	0.4	-0.1	0.1	-	-
		less - Net overseas migration	8.2	7.6	4.2	1.5	3.1	0.1	0.1	0.2	25.0
	equals - final ERP 30 June 2006		6 816.1	5 126.5	4 090.9	1 567.9	2 059.4	490.0	210.6	334.1	20 697.9
- nil or rounded to zero (including null cells)
(a) Includes Other Territories

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