Source: Economics Mock Exam (Ohio State University)
Tags: microeconomics, opportunity cost, elasticity of demand, price elasticity, monopoly, market structure, consumer behaviour, firm behaviour, scarcity, trade-offs, demand curve
Difficulty: Introductory. No prerequisites beyond basic maths. If you are comfortable with the idea that resources are limited and choices have consequences, you are ready for this material.
Microeconomics is the branch of economics that zooms in on the decisions of individual people and businesses, rather than looking at the economy as a whole. It asks questions like: why do consumers buy what they buy, how do firms decide what to charge, and what happens when markets do not work the way textbooks say they should?
This material sits at the foundation of nearly every other economics module. Concepts here (opportunity cost, elasticity, market power) show up repeatedly in intermediate micro, industrial organisation, and public economics. If you are joining the course late, start here before moving to macroeconomics.
Microeconomics studies how individuals and firms make decisions under scarcity. The three ideas that come up most often in exams are opportunity cost (what you give up when you choose), elasticity of demand (how sensitive buyers are to price changes), and monopoly power (what happens when one firm dominates a market).
Microeconomics
The study of how individual consumers and firms make decisions about allocating scarce resources. In simple terms, it is economics at the level of people and businesses, not countries.
Opportunity cost
The value of the next best alternative that must be forgone when a choice is made. Think of it as the price you pay in "what you could have done instead." It is not always measured in money.
Elasticity of demand (price elasticity of demand)
A measure of how much the quantity demanded of a good responds to a change in its price. In simple terms, it tells you whether customers will run away or barely notice when you raise the price.
Elastic demand
Demand where a change in price causes a proportionally larger change in quantity demanded. Luxury goods tend to fall here: raise the price of designer handbags, and sales drop sharply.
Inelastic demand
Demand where a change in price causes a proportionally smaller change in quantity demanded. Essential goods sit here: the price of insulin can rise and people still need to buy it.
Monopoly
A market structure in which a single firm is the sole seller of a product with no close substitutes. Think of it as one company with no meaningful competition in its market.
Market structure
The organisational characteristics of a market, including the number of firms, the nature of the product, and the ease of entry. It ranges from perfect competition (many firms, identical products) through to monopoly (one firm, unique product).
Microeconomics analyses the behaviour of individual consumers and firms.
It asks how buyers decide what to purchase and how much to pay.
It asks how sellers decide what to produce, how much to charge, and how to organise production.
This is distinct from macroeconomics, which looks at the economy as a whole (GDP, inflation, national employment).
The core assumption running through micro is scarcity: resources are limited, so every choice involves a trade-off.
Every decision has a cost, even when no money changes hands.
If you spend your evening studying for an exam rather than going to a film, the opportunity cost is the enjoyment you would have received from the film.
If a government spends its budget on defence, the opportunity cost is the schools or hospitals it could have built instead.
Opportunity cost only ever refers to the next best alternative, not to every possible alternative. You compare against the single best option you did not choose.
This concept is foundational. It appears in consumer theory, producer theory, and trade theory later in the course.
Elasticity measures responsiveness. Specifically, it captures the percentage change in quantity demanded divided by the percentage change in price.
Why it matters for businesses:
A firm selling an elastic good (luxury items, non-essential electronics) knows that raising prices will cause a large drop in sales. Pricing strategy needs to be cautious.
A firm selling an inelastic good (essential medications, petrol in areas with no public transport) can raise prices without losing many customers, though ethical and regulatory constraints may apply.
Elasticity is not a fixed property of a good. It depends on context:
The availability of substitutes (more substitutes = more elastic)
The proportion of income spent on the good (higher share = more elastic)
Time horizon (demand tends to become more elastic over longer periods as consumers find alternatives)
A monopoly exists when one firm is the sole seller in a market with no close substitutes.
Monopolies do not always lead to lower prices for consumers. This is a common exam trap.
Without competitive pressure, a monopolist can restrict output and charge higher prices than a competitive market would produce.
Some monopolies arise from natural advantages (utilities with high infrastructure costs), patents, or government-granted licences.
In some regulated cases, monopolies can deliver lower prices through economies of scale, but this requires active oversight. The default outcome, absent regulation, is higher prices and lower output.
Opportunity cost is the reason economists talk about the "guns vs. butter" trade-off in government spending: every pound or dollar spent on military hardware is a pound or dollar not spent on social services. Elasticity of demand is why airlines charge wildly different prices for the same seat, business travellers have inelastic demand (they need to fly on specific dates), while holiday travellers are elastic (they will switch dates or destinations for a cheaper fare).
Students often think opportunity cost means "the monetary cost of something." It does not. Opportunity cost is about what you give up, which may have nothing to do with money.
Students frequently confuse microeconomics with macroeconomics on definitional questions. Micro = individuals and firms. Macro = the economy as a whole. The prefix tells you the scale.
A common error is believing monopolies always harm consumers. While monopolies typically lead to higher prices, regulated natural monopolies (water utilities, for instance) can sometimes deliver lower costs than fragmented competition would.
Students sometimes treat elasticity as binary: elastic or inelastic. In practice, elasticity sits on a spectrum and varies with context.
⚠️ The distinction between micro and macro is a guaranteed early exam question. Know the definitions cold.
⚠️ Opportunity cost questions almost always require an example. Practise writing one in a single sentence: "The opportunity cost of X is Y, because Y is the next best alternative foregone."
⚠️ Elasticity questions often test whether you understand why it matters for pricing, not just the definition. Be ready to explain the business implications.
⚠️ The monopoly true/false trap ("monopolies always lead to lower prices") appears frequently. The answer is false, and you should be able to explain why in one or two sentences.
True or false: Microeconomics studies the economy as a whole.
Fill in the blank: Opportunity cost is the value of the ________ that must be foregone.
True or false: If demand for a good is inelastic, a price increase will cause a large drop in quantity demanded.
Fill in the blank: A market with only one seller and no close substitutes is called a ________.
True or false: Monopolies always result in lower prices for consumers.
Answers: 1. False 2. next best alternative 3. False (inelastic means quantity demanded is relatively unresponsive) 4. monopoly 5. False
Q: What is the main goal of microeconomics?
A: To analyse the behaviour of individual consumers and firms. It examines how they make decisions about the allocation of scarce resources, as opposed to macroeconomics, which studies the economy at a national or global level.
Q: Explain the concept of opportunity cost and provide an example.
A: Opportunity cost is the value of the next best alternative that must be foregone when a choice is made. For example, if you spend your evening studying for an exam rather than going to a film, the opportunity cost of studying is the enjoyment you would have received from the film.
Q: Define elasticity of demand and explain why it matters for businesses.
A: Elasticity of demand measures how much the quantity demanded of a good responds to a change in price. It matters because it guides pricing strategy. If demand is elastic (luxury goods), a price increase leads to a large drop in sales. If demand is inelastic (essential medications), consumers are less responsive to price changes, and the firm has more pricing power.
Q: True or false: Monopolies always lead to lower prices for consumers.
A: False. Monopolies typically lead to higher prices because the single seller faces no competitive pressure and can restrict output. While regulated monopolies or natural monopolies may sometimes deliver lower costs through economies of scale, the general expectation is that monopoly pricing exceeds competitive pricing.
Opportunity cost connects directly to comparative advantage in international trade: countries specialise in producing goods where their opportunity cost is lowest, not where they are most productive in absolute terms.
Elasticity of demand links to fiscal policy and taxation: when a government taxes a good with inelastic demand (cigarettes, petrol), the tax revenue is reliable because consumers do not reduce purchases much.
Monopoly and market structure lead into industrial organisation and competition policy, where you study how governments regulate firms with excessive market power.
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