An assessment of progress is made by examining data from 2008 (or closest to) until the latest available data at the time of reporting, in 2019. The baseline year is 2008 as this was the year in which the National Indigenous Reform Agreement was established. The Report uses most recent available data and limitations are indicated where appropriate in the Report. Some data sets have different sampling approaches and time-series, particularly in the use of comparison data for non-Aboriginal people (or whole-of-population). In some instances, comparable non-Aboriginal or Victoria-wide data is not available to support group comparisons.
In these instances, proxy data is used. For example, ABS data from Aboriginal-specific surveys such as the National Aboriginal and Torres Strait Islander Health and Social Surveys are used to inform some indicators. The most comparable equivalent data for non-Aboriginal Victorians is the Victorian Population Health Survey which has a different sampling approach and time series. This approach, while liable to sampling bias, has been used by Victorian population health researchers and is methodologically sound. Aboriginal data has unique challenges. Small population sizes mean that there is a diminished ability to detect trends and changes for a given outcome (minimum detectable effect), and a greater degree of data volatility leading to large fluctuations between time points. This means there is a higher threshold for determining improvement at a statistically significant level compared to general population data. The Report identifies where trends are suggestive of improvement or deterioration but are compromised by data volatility or small numbers.