Income
Individual income quartiles
About this topic
Individual income quartiles group people aged 15 years and over into four evenly sized income ranges so the distribution of personal income can be compared objectively across areas and over time. The quartile method focuses on relative position in the income distribution rather than raw dollar brackets.
This topic is useful because direct income amounts are affected by inflation and wider economic change. Quartiles provide a clearer way to compare whether an area is becoming relatively lower, middle, or higher income over time.
Interpretation notes
- This is a derived distribution of personal income for people aged 15 years and over, with each quartile representing a quarter of the income distribution.
- Quartiles show relative position rather than fixed dollar brackets, which makes them more robust for comparisons over time.
Key insight
In 2021, the lowest income quartile held the largest share among residents aged 15 and over in Cairnlea, accounting for 34.9%.
Section overview
Individual income quartiles
Cairnlea - Persons aged 15+ (Usual residence)
This table summarises individual income quartiles for Cairnlea in 2021 for persons, with comparison against Brimbank (C) and change since 2016.
Individual income quartiles snapshot
2021 distribution by category for Cairnlea, with comparison markers for Brimbank (C).
Lowest group
2021 count
2,688
% of total
34.9%
Change from 2016
+11.3pp
2,688
34.9%
+11.3pp
Medium lowest
2021 count
1,693
% of total
22.0%
Change from 2016
-4.8pp
1,693
22.0%
-4.8pp
Medium highest
2021 count
1,991
% of total
25.8%
Change from 2016
-4.9pp
1,991
25.8%
-4.9pp
Highest group
2021 count
1,333
% of total
17.3%
Change from 2016
-1.6pp
1,333
17.3%
-1.6pp
Chart view
Individual income quartiles change
Absolute change in category counts between 2016 and 2021.
Lowest group
+2,658
+11.3pp
Medium lowest
+1,659
-4.8pp
Medium highest
+1,952
-4.9pp
Highest group
+1,309
-1.6pp
Data table
Individual income quartiles for Cairnlea. Individual income quartiles. 2021 and 2016 counts, percentages, and change compared with Brimbank (C).
| Category | 2021 | 2016 | Change | |||||
|---|---|---|---|---|---|---|---|---|
| Count | % | Brimbank (C)% | Count | % | Brimbank (C)% | Count | pp | |
| Lowest group | 2,688 | 34.9% | 32.8% | 30 | 23.6% | 32.0% | +2,658 | +11.3pp |
| Medium lowest | 1,693 | 22.0% | 27.0% | 34 | 26.8% | 26.8% | +1,659 | -4.8pp |
| Medium highest | 1,991 | 25.8% | 24.8% | 39 | 30.7% | 25.6% | +1,952 | -4.9pp |
| Highest group | 1,333 | 17.3% | 15.4% | 24 | 18.9% | 15.6% | +1,309 | -1.6pp |
| Total persons aged 15+ | 7,705 | 100.0% | 100.0% | 127 | 100.0% | 100.0% | +7,578 | 0.0pp |