Forms of Market and Price Determination
Forms of Market and Price Determination tests how market structure shapes a firm's revenue curves and where equilibrium output is chosen.
Core rules
- Perfect competition: many buyers and sellers, homogeneous product, free entry and exit, perfect knowledge. The firm is a price taker, so AR = MR = price, a horizontal line.
- Monopoly: one seller, no close substitutes, strong entry barriers; AR slopes downward and MR falls below AR. MR = AR (1 − 1/Ed).
- Monopolistic competition: many sellers, differentiated products, selling costs, free entry.
- Oligopoly: a few large firms whose decisions are interdependent.
- Equilibrium of the firm: produce where MR = MC and MC is rising; if MR exceeds MC, expand; if MR is below MC, contract.
- Shut-down point: price = minimum AVC. Break-even point: price = minimum AC.
Worked example
A perfectly competitive firm faces a price of ₹10, so MR = ₹10. Its MC is ₹4 for the fourth unit, ₹8 for the fifth, ₹10 for the sixth and ₹13 for the seventh. The sixth unit adds exactly ₹10 of revenue and ₹10 of cost, so output is 6 units. A seventh unit would add ₹13 of cost against ₹10 of revenue and cut profit by ₹3.
Traps that cost marks
- Drawing a downward-sloping demand curve for a perfectly competitive firm; its demand is horizontal at the market price.
- Confusing 'no close substitutes' (monopoly) with 'differentiated products' (monopolistic competition).
- Writing that a monopoly can charge any price; it is limited by the demand curve and its elasticity.