Notes on data
- Over time, minor changes have been made to the method for counting cases of injury, therefore data presented in previous AIHW reports may not match the data presented in this report.
- Only a small proportion of all incidents of injury result in admission to a hospital. For each admission, many more people with injuries are treated in an emergency department (ED) but not admitted, or visit a general practitioner, physiotherapist or Urgent Care/Walk-in Clinic rather than a hospital. A larger number of minor injuries do not receive any medical treatment. A smaller number of severe injuries that quickly result in death do not include a stay in hospital but are captured in mortality data.
- This report only counts injuries that present to Australian hospitals or EDs. This report therefore underestimates the total burden of injuries among children as it does not count injuries where health care is not sought from a hospital or ED.
- Minor injuries (for example, scratches and bruises) are likely underrepresented in this report as injury hospitalisations or ED presentations are likely biased towards injuries perceived as severe enough to require health care intervention. By the same logic, injuries that are perceived as more serious (for example, head injuries) are likely to be over-represented in this report.
- The NHMD does not provide unique identifiers and this report is unable to present information about the number of people injured. We instead present information about the number of cases of injury.
- The COVID-19 pandemic and the resulting Australian Government closure of the international border from 20 March 2020, caused significant disruptions to the usual Australian population trends. This report uses Australian Estimated Resident Population (ERP) estimates that reflect these disruptions. In the year July 2020 to June 2021, the overall population growth was much smaller than the years prior and in particular, there was a relatively large decline in the population of Victoria. ABS reporting indicates these were primarily due to net-negative international migration (National, state and territory population, June 2021 | Australian Bureau of Statistics (abs.gov.au)). Please be aware that this change in the usual population trends may complicate your interpretation of statistics calculated from these ERPs. For example, rates and proportions may be greater than in previous years due to decreases in the denominator (population size) of some sub-populations.
- Overall, the quality of the data in the NNAPEDCD is sufficient to be published in this report. However, limitations of the data as listed in the NNAPEDCD technical notes should be taken into consideration when ED data are interpreted.
- The recording of external cause information is not as complete in the NNAPEDCD as the NHMD. A short list of ICD10 codes are used and the proportion of missing data is higher than the NHMD.
- The ED admission policy was changed for New South Wales (NSW) hospitals in 2017–18 and detailed in the NHMD technical notes. For NSW, the effect was a significant decrease (3.7%) in all public hospital admissions in 2017–18 compared to 2016–17. The impact of the change was felt disproportionately among hospitalisations for injury and poisoning. Due to the size of the contribution of NSW data to the national total, there is a break in series in Australian data from before and after 2017–18.