This document was added or updated on 22/10/2015.

EXPLANATORY NOTES - MODELLED ESTIMATES FOR SMALL AREAS

1 This publication also contains modelled estimates of disability and carers for small areas based on data from the 2012 Survey of Disability, Ageing and Carers (SDAC), 2011 Australian Census of Population and Housing, 2012 Estimated Resident Population (ERP), and aggregated administrative data from the Department of Social Services, 2012, sourced from 1379.0.55.001 - National Regional Profile, 2008 to 2012.

2 These modelled estimates for small areas were produced as a consultancy for the NSW Department of Family and Community Services, applying ABS methods and quality standards. This work is similar to a previous consultancy the ABS undertook in 2010 based on the 2009 SDAC.

3 The modelled estimates for small areas can be interpreted as the expected value for a typical area in Australia with the same characteristics. There will be differences between the disability or carer characteristic prediction and the actual number of people with that characteristic not accounted for in the measure of accuracy. One explanation for this is that significant local information about particular small areas exists, but has not been included in the model as it is not available to the ABS. It is important to consider local area knowledge, such as information on disability or carer related facilities and businesses in the area, when interpreting the modelled estimates for that region.

4 Used in conjunction with an understanding of local area characteristics and their reliability limitations, modelled estimates for small areas can assist in making decisions on issues, such as the requirement for services, relevant to disability and carer populations at the small area level. Care needs to be taken to ensure decisions are not based on inaccurate estimates. It is recommended that the provided modelled estimates for small areas are aggregated to larger regions (such as regional planning regions) as this will improve the accuracy of the estimates upon which decisions may be based.

POPULATION GROUPS

5 The modelled estimates for small areas are applicable to private dwellings in scope of the SDAC 2012 private dwellings collection. Data for special dwellings (approximately 14% of the total SDAC sample) was excluded. Please refer to the Notes tab within each spreadsheet for the population group each table of data relates to.

GEOGRAPHY

6 The level at which modelled estimates for small areas have been produced varies by jurisdiction, as follows:

	Small area level*
New South Wales	Local Government Area
Victoria	Statistical Area Level 2
Queensland	Statistical Area Level 2
South Australia	Statistical Area Level 2
Western Australia	Local Government Area
Tasmania	Local Government Area
Northern Territory	Statistical Area Level 2
Australian Capital Territory	Statistical Area Level 2

* Based on the ASGS, 2011, with 2012 concordance provided for LGA

METHODOLOGY

7 To produce accurate and detailed estimates of disability and carer characteristics at the small area level, models are created using the detailed SDAC data, in conjunction with the Census data, and 2012 ERP to produce modelled estimates for small areas. The modelling method assumes that the relationships observed at the higher geographic level (as available in SDAC) between the characteristics of interest and known characteristics also hold at the small area level. Section 2 of the SDAC 2012 Modelled Estimates for Small Areas Explanatory Notes pdf details the process used to produce modelled estimates for small areas.

RELIABILITY OF ESTIMATES

8 The errors associated with the modelled estimates for small areas fall into four categories. Sampling error, non-sampling error, modelling error, and prediction error. The relative root mean squared error (RRMSE) provides an indication of the deviation of the modelled estimate from the true value. The RRMSE is primarily a measure of prediction error, but in its calculation it also inherits some aspects of modelling and sampling error. Section 3 of the SDAC 2012 Modelled Estimates for Small Areas Explanatory Notes pdf provides details on the accuracy of results. Section 4 provides details on using the modelled estimates for small areas, including instructions for aggregating modelled estimates (with worked examples).

CONFIDENTIALITY

9 Estimates have been confidentialised to ensure they meet ABS requirements for confidentiality. Estimated counts, proportions, and confidence interval boundaries are adjusted and prefixed with a ‘<’ or ‘>’ to indicate that the unconfidentialised estimate is less than or greater than the value shown.

10 Because SDAC population benchmarks have been used in the modelling process, the modelled estimates provided here can also be considered perturbed. Users should note that due to perturbation, the summing, or aggregation, of the modelled estimates to derive a total (e.g. at state level) will not necessarily give the same result as the published total. In these cases, the difference between the sum of modelled estimates for small areas and the published total will be small and will not impact the overall information value of the aggregate total or any individual component.

11 Aggregation of the modelled estimates of small areas to capital city or state/territory level is not recommended. If you require capital city or state/territory level data for the characteristics of disability and carers provided here at small area level, then use of published data (or use of the TableBuilder product) is suggested.

ADDITIONAL INFORMATION

12 The SDAC 2012 Modelled Estimates for Small Areas Explanatory Notes pdf accompany the modelled estimates for small areas. We recommend reading the full content of this explanatory notes document to ensure the best and most appropriate usage of the data. If printing the explanatory notes we recommend colour, as content about using the data has been colour coded to assist with conveying the steps involved.