Forms of Market and Price Determination
Forms of Market and Price Determination covers perfect competition, monopoly, monopolistic competition and oligopoly. BIEAP tests market features, equilibrium conditions, price discrimination, and the welfare effects of market power.
Core rules
- Perfect competition: many buyers and sellers, homogeneous product, free entry and exit, perfect information. A firm is a price taker; price = AR = MR.
- Monopoly: single seller, no close substitutes, barriers to entry. The firm faces a downward-sloping demand curve; MR < AR.
- Monopolistic competition: many firms, differentiated products, free entry. Firms compete through product differentiation.
- Oligopoly: few large firms with interdependence; the kinked demand curve explains price stickiness.
- Profit-maximising equilibrium for all market forms: MR = MC and MC rising. In perfect competition this becomes P = MC.
- A firm shuts down in the short run if price falls below average variable cost.
Worked example
A monopolist faces demand P = 100 − 2Q, so TR = 100Q − 2Q² and MR = 100 − 4Q. If MC = 20, set 100 − 4Q = 20, giving Q = 20 and P = 60. The monopolist restricts output and charges above marginal cost.
Traps
Do not say a perfectly competitive firm sets price; it accepts the market price. MR = MC is the profit rule, but shutdown depends on AVC. Normal profit is included in economic cost, so zero economic profit is not a loss. Do not confuse product differentiation with identical products.