Statistical notes

Population rates

Population rates were calculated using the ABS estimated resident population (ERP) at the midpoint of the data range (for example, rates for 2022–23 financial year data were calculated using ERP at 31 December 2022, while rates for 2022 calendar year data were calculated using ERP at 30 June 2022).

Crude rates

A crude rate provides information on the number of events (for example, palliative care-related hospitalisations) relative to the population ‘at risk’ (for example, the entire population) in a specified period. No age adjustments are made when calculating such a rate and crude rates are used throughout this publication. Note that owing to the differences in approaches used to calculate population rates for different analyses, the rates shown throughout this report for Australia (sometimes labelled as the ‘Total’) may differ slightly from one analysis to another.

Age-specific rates

Age-specific rates provide information on the incidence of a particular event in a specified age group relative to the total number of people ‘at risk’ of that event in the same age group. It is calculated by dividing the number of events occurring in each specified age group by the corresponding population in the same group, and then multiplying the result by a constant (for example, 10,000) to derive the rate. 

Age-standardised rates

Age-standardised rates are rates that adjust the crude rate to eliminate the effect of differences in population age structures when comparing crude rates for different periods of time, different geographic areas and/or different population sub-groups (for example, between one year and the next and/or states and territories, Indigenous and non-Indigenous populations).

Direct standardisation was used in this report. To calculate age-standardised rates, age-specific rates (grouped in 10-year intervals, except for the age group of 0–14 and 85 and over) were multiplied against a standard population. Directly age-standardised rates were adjusted using the current Australian standard population (that is, the non-recast Australian estimated resident population (ERP) as at 30 June 2001).

Average annual rates of change

Average annual rates of change or growth rates have been calculated as geometric rates: 

Average rate of change=((Pn/Po)(1/n –1)) x 100. 

In this formula: Pn is the value in the later time period, Po is the value in the earlier time period and N is the number of years between the two time periods.

Descriptive analyses

Information presented in this report is based on descriptive statistics. When examining results, it should be considered that patterns of relationship between variables may be influenced by known and unknown confounding factors. Furthermore, relationships between variables do not necessarily reflect underlying causal links.

Patient day statistics

Patient day statistics can be used to provide information on hospital activity that, unlike hospitalisation statistics, accounts for differences in length of stay. As the National Hospital Morbidity Database (NHMD) contains records for patients ceasing hospitalisation during a specific reporting period (such as 1 July 2021 to 30 June 2022), this means that all patients who ceased hospitalisation during the reporting period are included, regardless of whether or not they were admitted during that period. Thus, not all patient days reported will have occurred during the reporting period. However, it is expected that, in general, patient days for patients who ceased hospitalisation in 2021–22, but who were admitted before 1 July 2021, will be generally counterbalanced by the patient days for patients still in hospital after 30 June 2022 who will cease hospitalisation in future reporting periods.