Forms of Market and Price Determination
What the domain tests
Forms of Market and Price Determination tests perfect competition, monopoly, monopolistic competition, and oligopoly, plus equilibrium under each. You must use MR = MC, identify normal and supernormal profit, and explain price discrimination and government price controls.
Core rules
- Perfect competition: many buyers and sellers, homogeneous product, free entry and exit, perfect information. The firm is a price taker; its demand curve is horizontal.
- Monopoly: one seller, no close substitute, entry barriers. The firm faces the downward-sloping market demand curve, so MR < AR.
- Monopolistic competition: many sellers with differentiated products; each firm has some price-setting power.
- Oligopoly: a few large firms; interdependence and strategic behaviour matter.
- Equilibrium: profit is maximised where MR = MC and MC is rising. In the short run a firm may earn supernormal profit, normal profit, or a loss; free entry removes supernormal profit in the long run under competition.
Worked example
A monopolist faces demand P = 20 − Q. TR = 20Q − Q², so MR = 20 − 2Q. If MC = ₹4, set 20 − 2Q = 4, giving Q = 8 and P = ₹12. At Q = 8, MR = MC = ₹4. The monopolist restricts output and charges a higher price than a perfectly competitive market would.
Traps that cost marks
Do not draw a horizontal demand curve for a monopoly. Do not say a monopoly has a supply curve independent of demand. Do not confuse shutdown, where price falls below minimum AVC, with exit, which is a long-run decision. Under monopolistic competition, product differentiation, not identical products, creates downward-sloping demand. Price discrimination requires market separation and different elasticities.