3101.0 - Australian Demographic Statistics, Mar 2012

Quality Declaration

ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 27/09/2012

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FEATURE ARTICLE 4: ADVICE ON THE USE OF 2011 PRELIMINARY REBASED ERP

INTRODUCTION

The ABS introduced a new methodology for processing the 2011 Census Post Enumeration Survey (PES), which enabled a more accurate measure of net undercount to be produced than had been possible in previous cycles. The lower net undercount which resulted from this change contributed towards a considerably larger intercensal error for the rebased Estimated Resident Population (ERP) than had been observed during previous rebasing periods.

PREVIOUS COMMENTARY ON THE ISSUE

While the official Estimated Resident Population (ERP) estimates are published in the June 2012 release of Australian Demographic Statistics (cat. no. 3101.0), the ABS appreciates that this larger than usual intercensal error presents a challenge for users who want to understand growth between 30 June 2006 and 30 June 2011. This was explored in detail in the technical note The impact of improvements to the 2011 PES on measuring population growth (2006-2011), which appeared in the December 2011 issue of Australian Demographic Statistics (cat. no. 3101.0) and is repeated in this publication. The discussion in the technical note, along with the advice given in this article, should be considered in relation to the specific requirements of users and the appropriateness of the advice for their needs.

FURTHER ADVICE

In understanding population growth between 30 June 2006 and 30 June 2011, the ABS advises that until the final rebased ERP estimates are released in June 2013, the comparison should focus on the published components of growth (births, deaths and net migration), rather than the difference between the official preliminary rebased population estimates for these reference periods.

Consistent with this advice, the ABS advises that subtracting these components of growth from the preliminary rebased 30 June 2011 ERP will provide an effective proxy for a reference point ERP for earlier reference dates back to September 2006. A table summarising this advice is available below.

Summary of advice provided for using 2011 preliminary rebased ERP (a)

User requirement	Level of geography
User requirement	Australia	States and territories	Sub-state
1. Level at 30 June 2011 (during the intercensal period and after June 2011)	Use preliminary rebased estimates (b)	Use preliminary rebased estimates (b)	Use preliminary rebased estimates (c)
2. Growth rates over the intercensal period	Use population growth components (b)	Use population growth components (b)	Areas with relatively low intercensal error - use preliminary rebased estimates (c) Areas with relatively high intercensal error - use change in previously published modelled data (d)
3. Growth rates over the intercensal period with reference to a level estimate within the intercensal period	Use population growth components (b) and for the reference point, subtract population growth components from 30 June 2011 preliminary rebased estimate to produce a proxy for a reference point ERP during the intercensal period that is consistent with the main estimate of interest - growth rates (b)	Use population growth components (b) and for the reference point, Subtract population growth components from 30 June 2011 preliminary rebased estimates, to produce a proxy for a reference point ERP during the intercensal period that is consistent with the main estimate of interest – growth rates (b)	Areas with relatively low intercensal error - use preliminary rebased estimates as the reference point Areas with relatively high intercensal error – use change in previously published modelled data (d) and for the reference point, subtract change in previously published modelled data from 30 June 2011 preliminary rebased estimates, to produce a proxy for a reference point ERP during the intercensal period that is consistent with the main estimate of interest – growth rates (c) (d)

(a) Users should consider the relevance of this advice to their specific requirements.

(b) Until final rebased estimates are released in Australian Demographic Statistics (cat. no. 3101.0).

(d) Modelled data for the intercensal period published prior to the release of preliminary rebased estimates can be found in the release of Regional Population Growth (cat. no. 3218.0), released on 30 March 2012.

While this approach is possible for ERP for Australia, and for all states and territories, some of the component data (eg. net overseas migration) are not available at the sub-state level.

For areas with relatively high levels of intercensal error in 2011, the ABS suggests using the 2006-2011 modelled growth as published in the March 2012 release of Regional Population Growth (cat. no. 3218.0) as a proxy measure for growth in these areas, until final rebased estimates are released in August 2013. For areas with relatively low intercensal error, the 2006-2011 growth indicated by the preliminary rebased estimates in the July 2012 release is more reliable.

OPTIONS BEING CONSIDERED

Users should note that the ABS is considering options for the methodological treatment of the large intercensal error for the 2006-2011 period, including the smoothing in of the impact of Automated Data Linking to the Post Enumeration Survey into the historical ERP series. This is outlined in Feature Article: ABS Treatment of Intercensal Error for 2006-2011. This treatment may further impact on growth, particularly for earlier intercensal time periods.