Difference in the relationship between health expenditure and income for Indigenous and other Australians is at least partially attributable to the more uniform poor health status of the former across income groups. While the lack of any association between income and Indigenous health status may simply reflect poor data quality, both in terms of income and self-assessed health status, there are two other possible explanations for the results: the Barker and social exclusion hypotheses.

The Barker hypothesis refers to the idea that adult mortality and morbidity may be related to foetal and infant life. In particular, it is proposed that diseases such as coronary heart, type 2 diabetes, central obesity and hypertension (all highly prevalent among Indigenous adults) originate through adaptations that the foetus makes to under-nutrition. Given the trajectory of Indigenous economic development since the 1960s, it is arguable that the present generation of Indigenous people in the upper income quintiles are far more likely than their non-Indigenous counterparts to have been exposed to the trifecta of low birthweight, poor nutrition and childhood disease that can reap such havoc in later life.

An alternative explanation to the Barker hypothesis is that current income is probably a poor proxy for socio-economic status among Indigenous people because they have been, and continue to be, socially excluded from mainstream society, irrespective of income. The main implication of both the Barker and social exclusion hypotheses (albeit for different reasons) is that it will take a long time to address the health deficits among Indigenous Australians. While the Barker hypothesis implies that there is a need to concentrate health expenditure on mothers and babies, the social exclusion hypothesis emphasises the need for ongoing support from both the community and governments across the entire lifecycle.