quintile

A proportion of a set of data that has been ranked and divided into five groups, each of which contains an equal number of data items. For example, Housing Affordability Stress is assessed for households in the bottom two quintiles (i.e. the bottom 40%) of the income distribution.

Q1 households are those earning in the bottom quintile (0–20%) of Australia's income distribution.

Q2 households are those earning in the second quintile (21–40%) of Australia's income distribution.