3101.0 - Australian Demographic Statistics, Dec 2017 Quality Declaration 
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 21/06/2018   
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FEATURE ARTICLE: FINAL REBASING OF AUSTRALIA'S POPULATION ESTIMATES USING THE 2016 CENSUS


INTRODUCTION

In this issue, the ABS finalised rebased population estimates for September 2011 - June 2016 using the results of the 2016 Census of Population and Housing. Final rebased estimates supersede all previously released estimates.

Rebasing estimated resident population (ERP) from the most recent Census count is a regular five-yearly exercise. It involves two main sets of calculations. The first set of calculations constructed a new ERP for 30 June 2016 from which quarterly ERP is calculated forward. This ensures that population estimates for the following intercensal period (2016-2021) are as accurate as possible, based on the most recent Census.

The second set of calculations revised the 19 intercensal quarterly estimates from 30 September 2011 to 31 March 2016. This ensures that the ERP time series for the previous intercensal period are comparable with later estimates.

Preliminary calculations were published in the December 2016 issue of Australian Demographic Statistics (cat. no. 3101.0), released on 27 June 2017. These calculations have now been finalised using more up-to-date component data. No further revisions are planned to be made to ERP up to and including 30 June 2016.


CONSTRUCTING THE FINAL ERP BASE FOR 30 JUNE 2016

The final rebased 30 June 2016 ERP is constructed from the 2016 Census count in three main steps.

1. Moving people back home

Firstly, people are counted by their place of usual residence rather than their place of enumeration. This accounts for interstate visitors on Census night and removes overseas visitors.

2. Including people who have been missed

The second step addresses people missed or counted more than once in the Census by:

  • adjusting for Census undercount and overcount using the results from the 2016 Census Post Enumeration Survey (PES);
  • adding in the number of Australian residents temporarily overseas (RTOs) on Census night using data on international travellers obtained from the Department of Home Affairs; and
  • applying demographic adjustments designed to resolve any other anomalies not accounted for in the PES or RTO adjustments.

3. Backdating from Census night to 30 June

The third step backdates the ERP at Census night (9 August 2016) to the ERP at 30 June 2016 by;
  • subtracting births;
  • adding deaths;
  • accounting for net interstate migration; and
  • accounting for net overseas migration.

The steps are illustrated in the following diagram:

Diagram: Constructing the final ERP base for 30 June 2016

The table below shows how the ABS arrived at 30 June ERP for Australia, states and territories after applying the adjustments above.

Adjustment Components of Estimated Resident Population, final - 30 June 2016

NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
Aust.(a)
Persons
'000
'000
'000
'000
'000
'000
'000
'000
'000

Components as at 9 August 2016:
Census count, actual location
7 565.0
5 946.1
4 844.5
1 674.8
2 517.8
504.2
259.1
400.6
23 717.4
plus - Residents absent interstate
84.6
99.4
56.2
31.9
23.7
15.5
5.5
13.0
330.1
less - Interstate visitors
73.4
45.7
113.6
15.6
35.9
6.8
26.8
11.4
330.1
less - Overseas visitors
95.9
73.1
83.9
14.4
31.2
3.0
9.0
4.9
315.5
equals - Census count, place of usual residence
7 480.2
5 926.6
4 703.2
1 676.7
2 474.4
510.0
228.8
397.4
23 401.9
plus - Allowance for under-enumeration(b)
59.2
86.1
60.6
3.0
9.5
0.3
12.0
-4.1
226.5
plus - Demographic adjustment
-3.0
-2.5
-2.0
-0.7
-0.9
-0.2
-0.1
-0.2
-9.6
plus - Residents temporarily overseas
212.9
179.0
92.1
35.4
75.5
7.9
5.2
11.1
619.0
equals - ERP as at 9 August 2016
7 749.3
6 189.2
4 853.9
1 714.3
2 558.5
517.9
246.0
404.2
24 237.9
Backdating components to 30 June 2016
less - Births
10.7
8.7
6.8
2.2
3.7
0.7
0.4
0.7
33.9
plus - Deaths
6.4
4.6
3.6
1.7
1.8
0.5
0.1
0.2
18.9
less - Net interstate migration
-1.0
1.3
1.5
-0.5
-1.1
-
-0.2
-
. .
less - Net overseas migration
13.1
10.7
4.1
1.5
1.7
0.2
0.2
0.6
32.0
equals - final ERP 30 June 2016
7 732.9
6 173.2
4 845.2
1 712.8
2 556.0
517.5
245.7
403.1
24 190.9

. . not applicable
- nil or rounded to zero (including null cells)
(a) Includes Other Territories - see Explanatory Note 2.
(b) Includes Census undercount and overcount from the 2016 PES and minor adjustments to address additional data coherence and quality matters.


COMPARISON TO PRELIMINARY REBASING

This process is the same as that followed to produce preliminary rebased ERP (published in June 2017). Final rebasing is primarily a process of revising preliminary rebased data to incorporate revisions to;
  • estimates of Residents Temporarily Overseas
  • components of population growth (births, deaths and migration) used to backdate from Census night to 30 June, and
  • demographic adjustments to address anomalies in the age and sex composition of the population.


Residents temporarily overseas

The preliminary residents temporarily overseas (RTO) estimates used the behaviour of travellers at the same time the previous year to predict the behaviour of people who were overseas on Census night. Final RTOs are based on actual traveller behaviour.


Backdating components

Preliminary rebasing used preliminary estimates of births, deaths and migration for the period 1 July - 9 August 2016. Components for this period have since been finalised, and the backdating recalculated to incorporate the new component estimates. For more information on the difference between final and preliminary components see the Explanatory Notes 7-22.


Demographic adjustment

In addition to the demographic adjustments made during preliminary rebasing, a further adjustment was made after analysing sex ratios by state/territory. This adjustment treated the distribution of the state/territory level population by sex in a comparable way to the treatment of age distribution and capital city/balance of state distributions, used for preliminary rebasing. The approach took a 60% weighting of the difference between male and female undercount estimates (from the PES) in 2016 and a 40% weighting of the same difference in 2011, and adjusted the male/female population within each state/territory accordingly. These adjustments were constrained to the total population for each state/territory, and to the total male and female populations for Australia.

Difference between preliminary and final estimated resident population, 30 June 2016

Final
Preliminary
Difference
'000
'000
'000
%

New South Wales
7 733
7 739
-6.4
-0.1
Victoria
6 173
6 179
-6.1
-0.1
Queensland
4 845
4 849
-3.7
-0.1
South Australia
1 713
1 713
-0.2
-
Western Australia
2 556
2 559
-3.0
-0.1
Tasmania
518
518
-0.1
-
Northern Territory
246
246
-0.1
-
Australian Capital Territory
403
403
-0.4
-0.1
Australia(a)
24 191
24 211
-19.9
-0.1

- nil or rounded to zero (including null cells)
(a) Includes Other Territories - see Explanatory Note 2.


REVIEW OF INTERCENSAL COMPONENTS OF GROWTH

As noted above, the final rebasing process affords the ABS an additional opportunity to revise births, deaths, interstate migration and net overseas migration (NOM) estimates for the five-year intercensal period with any updated data available to the ABS. In this final rebasing cycle, interstate migration and NOM were revised based on updated data. Births and deaths were not revised.


Revisions to interstate migration data

It is standard practice at final rebasing to revise the modelled interstate migration estimates during the intercensal period with data from Census questions related to an individual's place of usual residence one year ago, five years ago and at Census night. This process and its impact is detailed in the Technical Note 2: 2016 Census update of the net interstate migration model.


Revisions to net overseas migration data

Separate from usual rebasing, a new method of estimating NOM was introduced in the September 2017 issue of Australian Demographic Statistics released on the 22 March 2018 due to the removal of outgoing passenger cards by the Department of Home Affairs. Revising the 2011-2016 ERP for Rebasing has given the ABS the opportunity to incorporate revised quarterly NOM estimates, based on the new method. For more information on the new NOM estimation method see the Information Paper: Improvements to estimation of net overseas migration, Mar 2018 (cat. no. 3412.0.55.004).


INTERCENSAL DIFFERENCE

Intercensal difference is the difference between new Census-based ERP for 30 June 2016 and the ERP for the same point in time carried forward from the 2011 Census base using births, deaths and migration data.

Intercensal difference can be attributed to one or more of three sources;
  • the 30 June 2011 ERP based on the 2011 Census;
  • the rebased 30 June 2016 ERP based on the 2016 Census; and /or
  • the components of population change (births, deaths, interstate migration or overseas migration) during 2011-2016.

It is not possible to determine which of these sources have contributed to the intercensal difference. For this reason, population growth between 2016 and 2011 does not equal the sum of components of growth. The same is true for all periods prior to the most recent Census.

The intercensal difference for each state and territory, birth cohort and sex is assumed to have accumulated progressively over the five year period, with 1/20th of the total difference allocated to each intercensal quarter.

The table below shows the preliminary and final intercensal difference by number and percentage of total population for 2011-2016 for Australia, states and territories.

Preliminary and final intercensal difference(a), 2011 - 2016

Preliminary
Final
'000
%
'000
%

New South Wales
-10.0
-0.1
3.6
0.1
Victoria
-108.7
-1.8
-86.7
-1.4
Queensland
-6.9
-0.1
10.5
0.2
South Australia
-4.7
-0.3
-3.7
-0.2
Western Australia
57.4
2.2
37.9
1.5
Tasmania
1.4
0.3
7.2
1.4
Northern Territory
-0.5
-0.2
5.0
2.0
Australian Capital Territory
-7.1
-1.8
0.9
0.2
Australia(b)
-78.7
-0.3
-24.9
-0.1

(a) A positive number indicates that unrebased ERP as at 30 June 2016 was higher than rebased ERP. A negative number indicates that it was lower than rebased ERP.
(b) Includes Other Territories - see Explanatory Note 2.

The following table shows final intercensal difference by five year age groups.

Final intercensal difference by five year age groups(a), 2011 - 2016

Intercensal difference
'000
%

0-4
-9.9
-0.63
5-9
-37.2
-2.37
10-14
12.1
0.85
15-19
9.8
0.66
20-24
-10.2
-0.60
25-29
-23.7
-1.31
30-34
-5.0
-0.28
35-39
10.1
0.63
40-44
-3.3
-0.20
45-49
8.1
0.50
50-54
-5.7
-0.37
55-59
5.0
0.34
60-64
10.3
0.79
65-69
-7.6
-0.64
70-74
9.6
1.08
75-79
4.2
0.65
80-84
6.6
1.45
85 and over
1.8
0.38
All age groups
-24.9
-0.10

(a) A postive number indicates that unrebased ERP as at 30 June 2016 was higher than rebased ERP. A negative number indicates it was lower than rebased ERP.


FURTHER DATA RELEASES

Following this issue which contains final population estimates for Australia, states and territories based on the 2016 Census, it is expected that no subsequent revisions to the 2011-2016 intercensal period will be made.

Final rebased sub-state estimates for 2012-2016 will be published on 31 August 2018 in Regional Population Growth, Australia, 2016 (cat. no. 3218.0) and Population by Age and Sex, Regions of Australia, 2016 (cat. no. 3235.0).

Final rebased estimates of the Australian Aboriginal and Torres Strait Islander population at 30 June 2016 will be published in Estimates of Aboriginal and Torres Strait Islander Australians, 2016 (cat. no. 3238.0.55.001) on 31 August 2018.

Australian Demographic Statistics, March 2018 (cat. no. 3101.0) will be released on 20 September 2018 and will contain updated summary tables from the two above mentioned releases.