In terms of primary/secondary/tertiary sectors and private/public sector, and the relative size of firms.
How changes in demand and supply, relative bargaining strengths, discrimination and government policy can all influence differences in earnings between workers whether they are: skilled/unskilled; primary/secondary/tertiary; male/female; private sector/public sector. Definition, drawing and interpretation of diagrams that illustrate the effects of changes in demand and supply in the labour market.
Locally, nationally and internationally.