Context
This is the second of a series of posts on inequality, with a particular focus on South Australia. The first post highlighted differences in the share of the national household income going to different states, and the long-term decline in South Australia’s share of household income.
This post shows that, while household income may be lower than other states (except Tasmania), the distribution of income between households in South Australia is more equal than the national average.
Again, unless otherwise stated, the data here is drawn from the ABS Household Income and Wealth series. However, the data on the “share of total income” that I flagged as crucial in my previous post is less important here because the proportion of households in each quintile is the same. That is, there is no dynamic from changing population numbers.
The ABS Data on Inequality in South Australia
While the overall pattern of income distribution and inequality within South Australia is similar to the national pattern, by almost all measures in the ABS data, income distribution within South Australia is slightly more equal than for the country as a whole.
The table below summarises key measures for both gross household income, and for equivalised disposable income (that is, after-tax income adjusted to equivalent household sizes).
The first line is the income share of the lowest two income quintiles, with those households in South Australia having a slightly higher share than the national average.
The second line is the P90/P10 ratio which refers to the ratio of income of high and low income households, specifically, high-income households at the top of the 90th percentile by comparison with those in the 10th income percentile. These high-income households in South Australia received 8.19 times the gross income of households at the low (10th percentile) end of the income spectrum. This represents significant inequality within South Australia, although it is less than the Australian average ratio of 8.98.
The third line is the Gini Coefficient, which is a complex statistical measure where lower numbers represent more equal income shares (0 would be perfect equality, and 1 would be absolute inequality with one person receiving all income). While the Gini coefficient is widely used, I don’t find it particularly useful. The number is meaningless of itself (I still have to look it up every time I see it) and the importance of a difference at the second or third decimal point is hard to grasp. Again though, the Gini Coefficient shows SA has a slightly more equal income distribution than the national average.
It is also worth noting that in each case, the equivalised disposable income figures are much more equal than the gross income figures. This demonstrates the importance of both household size and the redistribution impact of taxes. But in each metric in both gross and equivalised data sets, the South Australia figures are slightly more egalitarian than the national ones.
Top End Drivers
It is important to note that the differences between South Australia and the country as a whole are not the same across all income quintiles. The incomes of those on the lowest incomes in South Australia are much closer to those on the lowest incomes nationally than is the case for those in the highest income brackets. The average (equivalised disposable) income of the lowest income quintile households in South Australia was $403p.w. in 2019-20. This was 97% of the national figure for the lowest income quintile. By contrast, for the highest income quintile, the average income in South Australia ($2,015p.w.) was only 90% of the national figure.
The same pattern is evident in the graph below, which shows the income at the top of the selected percentiles. The gap between South Australia and the national average increases as we move up the income spectrum. (The equivalised data provides a more like for like comparison, but the gross data [not plotted below] shows proportionately higher incomes at the top of the range in South Australia. The difference in the two data sets suggests that that relatively higher incomes in gross data are driven by larger household sizes rather than higher individual incomes).
This overall pattern is perhaps not surprising given that the incomes of many of those in the lowest income brackets are set nationally (e.g. social security and minimum wages) and are the same regardless of location. However, the patterns do highlight a key issue in the analysis of inequality – the importance of what is happening at the top end. In this case, it appears that the incomes at the high end of the South Australian spectrum are much lower than those evident in the national data. This reduces income inequality in South Australia, but also contributes to South Australia’s relatively low income share overall.
Census Data
The recent Census data provides a different perspective on the same phenomenon. The census only collects data in brackets of total household income, but the graph below shows the proportion of households in each bracket. South Australia has proportionately more households in the low-to-middle income brackets, but proportionately fewer in the brackets over $2,500 income per week. In particular, the top income bracket has the biggest gap of any bracket, with 12.4% of households nationally receiving more than $4,000 per week, by comparison with only 8% of South Australian households.
In short, the rich and super-rich don’t live in South Australia (or at least not in the same numbers as elsewhere in the country).
Inequality in South Australia Over Time
While my previous post highlighted a long-term decline in South Australia’s share of national household income, the changes over time in inequality within South Australia have been less clear. The graph below shows both the P90/P10 ratio (on the left axis) and the income share of the lowest income quintile (right axis) since 1994/95. Some caution is needed as there were methodological and data series changes in 2003-04 and 2007-08, but both indicators have remained fairly steady over the last 25 years.
The blue line of the P90/P10 ratio does show an increase in inequality in South Australia between high and low income markers from the mid-1990s until the Global Financial Crisis in 2007-08. However, the income gap began closing from that point until 2013-14 when inequality began rising again – at the same time as the income share of the lowest quintile began to fall. It remains to be seen if this is simply a fluctuation or the beginning of a period of further rising inequality. But at a minimum, we can say that the level of inequality in South Australia is long-standing and not getting any better.
Conclusions and Caveats
In summary, the data above shows that while South Australia is not getting an even share of national household income, inequality within SA is at least a little less than the national spread. Crucially though, both these phenomena appear to be driven at least in part by a proportionate lack of high-income households.
Again, all this data comes with caveats around the limitations of analysis by income quintile (and the lack of accounting for non-cash incomes). In particular, the crucial top 1% of income earners are invisible in the ABS data.
Perhaps though, the biggest caveat is that South Australia is not a singular entity and the analysis above is based on only one formulation of income inequality (between households). There are other important ways to consider income inequality beyond households, and there are also geographic differences within South Australia. These will be the subject of future posts in this series.