- Numbers: cell sizes less than 5 are obfuscated in line with ethics and data custodian requirements. Some other categorical data may also be obfuscated if a category can be calculated by subtracting any remaining categories from the total.
- Rates: rates are crude rates, which can allow for adjustment of population sizes across different areas, however these do not adjust for certain demographic attributes (specifically age and sex). The advantage to using crude rates is particularly important from a policy perspective, to understand what is influencing the rates. For example, it is important for policy and services to be aware if an area has more men and younger people.
- Population estimates: ABS estimated resident population (ERP) on age, sex and statistical local areas is used throughout AODstats based on calendar year of data. For financial year datasets, the earliest year is used (e.g. 2012/13, 2012 ERP is used).
There are limitations to using administrative data for purposes other than what it was originally intended when collected. This includes:
- Incomplete or missing data and inadequate coding.
- Some drugs are already in pre-determined drug categories and it is not possible to group them differently or include more specific drug information. In addition, sometimes drug information is not collected and therefore surrogate measures are used. The limitation to this is there will be events that are missed when they should be included and conversely events included when they should not be.
- Location information is dependent upon dataset and the majority of times LGA is the smallest area provided, and sometimes only state based data is available.
- Crude rates are used, which do not allow for certain demographic attributes (age and gender) to be compared accurately across areas, and also rates based on small numbers can produce unstable results.