Microeconomics 101 —
Exam Strategy and Key Concepts

Microeconomics 101 is logical, not mathematical. If you understand the reasoning behind each concept, the calculations follow naturally. The biggest mistake students make is memorising diagrams without understanding what they represent. Tour guide focuses on the logic.

Supply and Demand — The Engine of Microeconomics

Every micro exam has at least one supply-and-demand question. Master tour framework completely:

• Demand Law: Higher price → lower quantity demanded (negative relationship). Demand curve slopes downward
• Demand Shifts (NON-price factors): Income, preferences, prices of substitutes/complements, number of buyers, expectations — these SHIFT the whole curve
• Supply Law: Higher price → higher quantity supplied (positive relationship). Supply curve slopes upward
• Supply Shifts: Input costs, technology, number of producers, government policy, weather (for agriculture)
• Equilibrium: Price where quantity demanded = quantity supplied. Market "clears" — no shortage or surplus

Elasticity — Four Types You Must Know

• Price Elasticity of Demand (PED): % change in Qd ÷ % change in Price. |PED| > 1: elastic (luxury). |PED| < 1: inelastic (necessities). Elastic demand: price increase → TR falls. Inelastic: price increase → TR rises
• Income Elasticity (YED): Positive = normal good (income rises, demand rises). Negative = inferior good (income rises, demand falls)
• Cross-Price Elasticity: Positive = substitutes. Negative = complements
• Price Elasticity of Supply (PES): How responsive supply is to price changes. More elastic in long run

Market Structures — The Big Four

Learn them as a spectrum from most to least competitive:

• Perfect Competition: Many sellers, identical products, free entry/exit, price takers. Long-run: P = min ATC (zero economic profit). P = MC (allocatively efficient)
• Monopolistic Competition: Many sellers, differentiated products, free entry/exit. Short-run: economic profit possible. Long-run: zero economic profit (like perfect competition). Excess capacity — operates left of min ATC
• Oligopoly: Few sellers, interdependence. Kinked demand curve explains price rigidity. Game theory (prisoner's dilemma, Nash equilibrium) explains why firms don't collude optimally
• Monopoly: One seller. Sets P > MC (DWL — deadweight loss). No close substitutes. Barriers to entry. Can price discriminate

Consumer Theory — What Drives Demand

• Total Utility: Total satisfaction from consuming a good
• Marginal Utility: Additional satisfaction from consuming one more unit
• Law of Diminishing Marginal Utility: Each additional unit provides less additional satisfaction than the previous one. Tour explains why demand curves slope downward
• Consumer Surplus: Difference between what consumers are willing to pay and what they actually pay. Area above price, below demand curve

Externalities and Market Failure

• Negative externality: Third parties bear a cost they didn't agree to (pollution). Market overproduces — output is above socially optimal level. Solution: tax, regulation, property rights
• Positive externality: Third parties receive a benefit (education, vaccination). Market underproduces. Solution: subsidy
• Public goods: Non-excludable and non-rival (national defence). Market will underprovide — free rider problem
• Coase theorem: If property rights are clear and transaction costs are zero, parties can negotiate to efficient outcome regardless of who has the rights

Exam Answer Structure for Diagram Questions

When asked to use a diagram: (1) Draw it clearly and label ALL axes, curves, and points. (2) Explain what the diagram shows. (3) Show the change with arrows. (4) Identify the new equilibrium. (5) State the effect in words. Diagrams without labels get zero marks in most universities.

The three concepts that underpin everything else

Microeconomics builds on three foundational ideas that appear in every other concept. First: opportunity cost — every choice involves giving up something else, and rational decision-making means choosing options where the benefit exceeds the opportunity cost. Second: marginal analysis — economic decisions are made at the margin (should I produce one more unit? consume one more item?) and the answer is yes as long as the marginal benefit exceeds the marginal cost. Third: supply and demand — prices coordinate the behaviour of buyers and sellers, and changes in supply or demand shift prices and quantities in predictable directions.

Once these three ideas are solid, concepts like consumer surplus, producer surplus, price elasticity, market equilibrium, and market failure all become logical extensions rather than separate topics to memorise.

Graphs: draw them every time

Microeconomics is inseparable from graphs. Supply and demand diagrams, indifference curves, production possibility frontiers, cost curves (ATC, AVC, MC) — these are not illustrations of the concepts, they are the concepts expressed visually. Exam questions that ask you to 'analyse the effect of a minimum wage' or 'explain why a monopolist is allocatively inefficient' require you to draw the relevant diagram and annotate it. A verbal answer without a diagram earns partial marks at best in most economics assessments.

South African context for microeconomic concepts

South Africa provides particularly rich real-world examples for microeconomic concepts. The labour market (high unemployment, minimum wage legislation, collective bargaining) illustrates supply and demand in factor markets. Eskom's monopoly on electricity generation illustrates monopoly pricing and deadweight loss. The formal-informal sector divide illustrates barriers to market entry. Bringing South African examples into your answers demonstrates genuine understanding rather than textbook recitation.

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