Median
The middle value when everything is put in order: half the values are above it and half below. Census figures for age, income, rent and mortgage repayments are published as medians because a few very large values would distort an average.
Median and average
An average (or mean) adds everything up and divides by the count, so a handful of very high values pulls it up. A median takes the middle value and isn't moved by the extremes. Incomes, rents and repayments all have a long tail of high values, which is why the ABS publishes them as medians.
At the 2021 Census, the national medians were 38 years of age, $1,746 a week in household income, $375 a week in rent and $1,863 a month in mortgage repayments.
How Census medians are worked out
The Census collects most money questions in ranges rather than exact dollars, and publishes counts of people or households in each range. The ABS calculates its published income medians from those ranges, drawing on its Survey of Income and Housing. Age is collected exactly, and the ABS publishes median age in whole years.
Why medians can't be averaged
Medians don't combine the way counts do. The median for two suburbs together isn't the average of their two medians, or even a population-weighted average of them. It depends on how many people or households each has and how their values are spread.
To find the median for a combined area, add up the counts in each range across all the areas, then find the range where the middle value falls. This is the method to use for trade areas, sales territories and any other area built from several standard ones.
Medians in Censible
Censible calculates every median from the counts in each range, in the same way for a standard area, a group of areas or a catchment you draw, so a combined area gets its own median rather than an average of medians.
Its figures can therefore differ slightly from the ABS's published ones. Median age is shown to one decimal place, where 38.5 means halfway through age 38, while the ABS publishes whole years, so Censible's figure is usually about half a year higher. Mortgage repayments are collected in wide ranges, so Censible's median can differ from the ABS's by up to about $100 a month.
Median household income
The middle value of total household income in an area: half of households receive more and half receive less. At the 2021 Census, Australia's median household income was $1,746 a week before tax, or about $90,800 a year.
Housing stress
When a household spends more than 30% of its income on rent or mortgage repayments. A stricter definition, the 30/40 rule, only counts households in the bottom 40% of incomes, because higher earners can usually afford to spend more.
Median weekly rent
The middle weekly rent paid by households renting their home, from the Census: half pay more and half pay less. It covers renting households in occupied private dwellings, private and public, on existing as well as new leases. At the 2021 Census, Australia's median weekly rent was $375.
Area weighting (apportioning)
A way to estimate figures for an area that doesn't match published boundaries, by giving it a share of each overlapping area's counts. The share can follow land area, population or dwellings, and each assumes the figure is spread evenly within what it measures.
Questions people ask
An average adds all the values and divides by how many there are. A median is the middle value once they're in order. A few very high values raise an average but leave the median where it is.
Income, rent and mortgage repayments have a small number of very high values that would pull an average up. The median describes the typical household more fairly.
No. The median of a combined area depends on how many people each area has and how their values are spread. Add up the counts in each range across the areas and find the middle again.
Censible calculates medians from the counts in each range, which lets it give true medians for combined areas and catchments. Median age is shown to one decimal place rather than whole years, and mortgage medians can differ by up to about $100 a month because the ranges are wide.