This chapter considers some core concepts relating to production and productivity (they are not the same!) which will be useful in understanding the theory of market supply. Productivity is a measure of efficiency and changes in productivity have an important effect on the unit costs of supply. In this section we also briefly cover fixed and variable costs and the sources of some long run economies of scale which benefit bigger businesses as they expand. Specialisation is an important AS concept – be ready to apply it to the production possibility frontier for example.