The ABS has determined that a quality indicator will be developed to advise users about the reliability of a correspondence. The quality indicator will be incorporated in geographic correspondences produced from June 2012 onwards. There will be two indicators reported for each correspondence. There will be an overall indicator of how well the ABS expects a correspondence to convert data, and an individual indicator will also be provided for each "To" record. This will allow users to see where the data is likely to be converted accurately, and conversely where the converted data is most likely to cause issues. However, the indicator should be used as a guide only and caution should always be used when examining the results of data that is converted using correspondences.
The quality indicator is calculated by creating a ratio of the area that is being donated, as a proportion of the whole "From" area. The area that is being donated is then proportioned against the whole of the "To" area to create another ratio. These two ratios are then multiplied together. This process is repeated for each "From" area and the resulting ratios are then aggregated to form the overall figure. From these ratios a textual description is then applied to each "To" area, and an overall description for the entire geographical correspondence is derived from averaging the ratios of every "To" area.
The quality indicator provides a considered measure of the quality of the correspondence in relation to the weighting unit. However, it cannot take into account the nature of the data that is to be converted. Data that is similarly structured to the weighting unit (e.g. population-based data when the weighting units are based on population distribution) will convert accurately, but that will not follow for data that has no relationship to the weighting unit.
The textual descriptions that will be applied are as follows:
Good - The ABS expects that this correspondence or record will convert data overall to a high degree of accuracy and users can expect the converted data will reflect the actual characteristics of the geographic areas involved.
Acceptable - The ABS expects that this correspondence or record will convert data to a reasonable degree of accuracy, though caution needs to be applied as the quality of the converted data will vary and may differ in parts from the actual characteristics of the geographic areas involved.
Poor - The ABS expects that there is a high likelihood the correspondence or record will not convert data accurately and that the converted data should be used with caution and may not reflect the actual characteristics of many of the geographic areas involved.
There will be some cases where the ABS deems that a correspondence is not of an acceptable overall quality. In these cases they will be deemed as not being fit for purpose and will not be released. The ABS will release a series of correspondences from mid 2012 and these will be available, either for download or by email, free of charge from the ABS website. A list of correspondences that will be available can be found on the 'Correspondences' chapter of the ABS Statistical Geography web site: http://www.abs.gov.au/geography. The ABS will also produce custom correspondences, based on user requests, to convert data to the ASGS.