Quarterly estimates of interstate migration are published in National, state and territory population.
The main input to interstate estimates is Medicare change of address information supplied by Services Australia.
The Medicare system covers:
- Australian citizens
- permanent residents
- certain temporary visa holders.
The Medicare system excludes people on international student visas or temporary work visas (482).
Some people, particularly younger adults, do not register changes of address with Medicare or do so long after they move. This means that the Medicare data underestimates interstate migration for certain age groups.
Comparing Census and Medicare data over time shows that the level of under-reporting in Medicare changed between 2016-2021.
- This coincides with the uptake of COVID-19 vaccinations in 2021 across several states and territories, which changed usual Medicare reporting behaviour.
- Young adult males are more likely to be under-represented in the Medicare address change data, and across states and territories.
- Additionally, there was an increase in electronic Medicare claiming options at the doctor's office, online and by mobile phone app. This increased under-reporting of address change. Under-reporting was previously confined mainly to young adults aged under 30, but over time has increasingly affected older ages.
The below graph shows the number of people who reported in the Census that their address one year ago was interstate from their current address, divided by the number of address changes supplied to Medicare for the same year. A ratio higher than one suggests that more people reported in the Census that they had moved interstate than had reported their move to Medicare.
(a) Moves over one year, Census data weighted to ERP, Medicare data unadjusted.
(b) 2021 uses the ratio derived from 2016-2020 Census-based estimates of NIM divided by Medicare of the same period. This is to reduce COVID effects and allow a fair comparison with previous Census years.
Despite these limitations, Medicare data is the most effective source of quarterly internal migration currently available, based on timeliness and population scope. To address some of these known limitations, we also take Defence force movements and Census 1 year ago data to supplement Medicare.