Market structures - Economics IB Study Notes

Market structures describe how markets are organized based on the number of firms, type of product, and barriers to entry. The four main structures are perfect competition, monopolistic competition, oligopoly, and monopoly.

Perfect Competition features many small firms selling identical products with no barriers to entry. Firms are price takers (accept market price). Key characteristics: homogeneous products, perfect information, freedom of entry/exit. In long-run equilibrium: P = MC = AC (allocative and productive efficiency).

Monopolistic Competition has many firms selling differentiated products with low entry barriers. Firms have some price-setting power due to product differentiation. Long-run equilibrium: P > MC (not allocatively efficient) and firms produce at excess capacity.

Oligopoly involves few large firms dominating the market with high barriers to entry. Firms are interdependent - each firm's decisions affect rivals. Features include non-price competition, potential for collusion, and kinked demand curve theory explaining price rigidity.

Monopoly exists when one firm controls the entire market with prohibitive entry barriers. The monopolist is a price maker, facing the market demand curve. Produces where MR = MC but charges price from demand curve, resulting in P > MC (allocative inefficiency) and deadweight loss.

Key Formula: Profit maximization for all structures: MR = MC

Concentration Ratio: Measures market share of largest firms (e.g., 4-firm concentration ratio). Above 60% suggests oligopoly.

Memory Aid - BPNE: Remember market structures by Barriers, Product type, Number of firms, and Efficiency outcomes.

Understanding market structures is like understanding different restaurant ecosystems in a city.

Perfect Competition resembles agricultural markets - wheat farmers cannot individually influence wheat prices. The commodities market (gold, oil) operates similarly. Think of currency exchange: your holiday money exchange doesn't affect the pound-dollar rate. Each seller accepts the prevailing market price because their output is insignificant relative to total market supply.

Monopolistic Competition mirrors your local high street: coffee shops (Starbucks, Costa, local cafés) sell differentiated coffee. Each has unique branding, atmosphere, and loyalty, allowing slight price variations. The restaurant industry exemplifies this - thousands of restaurants compete, but each offers unique experiences. Clothing retailers, hairdressers, and takeaways all operate in monopolistically competitive markets.

Oligopoly dominates modern economies. The 'Big Four' UK supermarkets (Tesco, Sainsbury's, Asda, Morrisons) control ~70% market share. When one reduces prices, others respond immediately - classic interdependence. The smartphone industry (Apple, Samsung) shows non-price competition through innovation and branding. Airlines, telecommunications, and soft drinks (Coca-Cola vs Pepsi) are textbook oligopolies. The OPEC cartel demonstrates explicit collusion in oil markets.

Monopoly examples include local utility companies before privatization, Network Rail (UK rail infrastructure), and patent-protected pharmaceuticals. Microsoft's dominance in operating systems historically created near-monopoly conditions. Natural monopolies arise when high fixed costs make single-firm operation most efficient (water supply, electricity grids).

Analogy: Market structures are like school sports leagues - perfect competition is everyone eligible to compete; monopolistic competition adds team colors/styles; oligopoly is a premier league with few top teams; monopoly is one undefeated champion with no challengers allowed.