Market Structures

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Market structure classifies how a market is organised based on number of sellers, product differentiation, barriers to entry, and information availability. The CMA Foundation syllabus places this in Paper 3 (Business Economics and Business Statistics) under Economics at roughly 3% weight, usually as MCQ identification of market types.

Perfect Competition: many sellers, homogeneous product, price taker, AR = MR.
Monopoly: single seller, strong barriers, price maker, P > MR.
Oligopoly: few interdependent sellers, kinked demand curve, price rigidity.
Monopolistic Competition: many sellers, differentiated products, downward-sloping demand.

Must-know formulas: TR = P × Q, AR = TR / Q = P, MR = ΔTR / ΔQ, Profit maximisation: MR = MC, Shut-down point: P = AVC.

🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Classification Criteria

Four traits decide where a market sits on the competition spectrum: seller concentration, product nature (homogeneous vs differentiated), barriers to entry and exit, and knowledge symmetry. Perfect competition sits at one extreme and pure monopoly at the other; oligopoly and monopolistic competition fill the middle.

Revenue Curves by Market Type

Market Type	Demand Curve	AR vs MR	Price Maker/Taker
Perfect Competition	Horizontal at P	AR = MR = P	Price taker
Monopoly	Downward sloping	AR > MR; P > MR	Price maker
Oligopoly	Kinked demand	AR > MR (with notch)	Price maker (strategic)
Monopolistic Competition	Downward sloping	AR > MR	Price maker (limited)

Profit Maximisation and Shut-Down Rule

A firm chooses output where MR = MC. In the short run, the firm continues to operate if P ≥ AVC and shuts down if P < AVC. In the long run, the condition for survival becomes P ≥ AC, because economic profit attracts entry under free-entry markets.

Long-Run Equilibrium Outcomes

Under perfect competition: P = MC = AC, so normal profit only, with both productive efficiency (lowest AC) and allocative efficiency (P = MC).
Under monopoly and monopolistic competition: P > MC, so allocative inefficiency persists.
Under oligopoly: outcomes depend on whether firms collude (cartel acts like monopoly) or compete.

Common exam traps include treating oligopoly as one model rather than a family (collusive, non-collusive, price leadership, kinked demand) and forgetting that AR = MR only under perfect competition.

🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Price Discrimination in Monopoly

A monopolist can practise three degrees of price discrimination if it has market power and can prevent resale:

First degree (perfect): charges each consumer their maximum willingness to pay; turns consumer surplus into producer surplus.
Second degree: quantity discounts or block pricing (e.g., bulk-purchase slabs).
Third degree: different prices across identifiable market segments (e.g., student vs adult cinema tickets).

Worked Micro-Example

A monopolist faces demand P = 100 − Q (₹ per unit) and total cost TC = 20Q + 200 (₹).

TR = (100 − Q)Q = 100Q − Q², so MR = 100 − 2Q.
MC = dTC/dQ = 20.
Setting MR = MC: 100 − 2Q = 20 → Q* = 40 units.
P* = 100 − 40 = ₹60.
Profit π = (60 − 20)(40) − 200 = ₹1,400.

This single calculation tests the MR = MC rule, the link between AR (which equals P) and MR, and the π = (P − ATC) × Q formula — three items that frequently appear as MCQs in Paper 3.

Common Mistakes and Exam Strategy

Confusing break-even (P = AC) with shut-down (P = AVC): break-even is a long-run condition, shut-down is short-run.
Assuming monopolistic competition has zero profit in the short run — it can earn supernormal profit until entry erodes it.
Treating the kinked demand curve as stable; the kink assumes rivals match price cuts but ignore price rises.
For Paper 3 weighting, target one MCQ per concept: identification, AR/MR relationship, profit-maximisation rule, long-run outcome.

Practice Prompts

If AR = ₹80 and elasticity of demand Ep = 2, what is MR under monopoly?
Under perfect competition in the long run, why does P = MC also imply zero economic profit?

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Market Structures