Data is derived from the Household Labour Force Survey (HLFS) through the Integrated Data Infrastructure.
Underutilisation is a measurement of labour force efficiency. It combines those working but seeking more hours of work (underemployment), those seeking work (unemployment), as well as those who aren't seeking working but would either take a job if offered or will start seeking work soon (potential labour force).
The HLFS does not capture those those who are employed under their skill level, e.g. someone working in a fast food chain with a masters degree in engineering.