while the concept of underlying need refers to the health workforce (size and mix) that will meet societal health sector objectives (including equity) in an efficient manner. In the context of market failure as typifies the health sector and the health labour market, concepts of expressed demand and underlying need are likely to depart. In a health workforce planning exercise, it is the underlying health workforce need, which in turn reflects the need for health care – including health promotion – that should drive supply, not expressed demand. We also note that the latter concept being mediated by supply is not exogenous.