Underemployment - Japan's army of under-employed ex-housewives
This is a lovely example of what is meant by the term 'under-employment' and illustrates exactly what this implies for an economy.
In this case, Japan is used as our case study, with rigidities - and downright sexism - meaning that many ex-housewives cannot find a job commensurate with their qualifications.
As a result, many highly qualified women struggle to re-enter the labour force despite policy initiatives like Shinzo Abe's "Womenomics", and Japan's productive capacity suffers as a result.
Female labour market participation rates in Japan are among the lowest for all advanced, high-income countries.