Microeconomics — Eduqas A-Level Economics

Q: What is the difference between a movement along and a shift of the demand curve?

A movement along the demand curve occurs when the price of the good itself changes, leading to a change in quantity demanded (ceteris paribus). A shift of the demand curve happens when a non-price factor changes, such as income, tastes, or the price of related goods. For example, an increase in income shifts the demand curve for normal goods to the right, meaning at every price, consumers demand more.

Q: How do I calculate profit maximisation output?

Profit is maximised where marginal revenue (MR) equals marginal cost (MC). In perfect competition, price equals MR, so the condition is P=MC. In imperfect competition, MR is less than price, so you find the output where MR=MC, then charge the price from the demand curve at that output. Remember to check that price is above average variable cost in the short run, otherwise the firm should shut down.

Q: What are the main types of market failure?

The main types are: (1) Externalities – costs or benefits that affect third parties not involved in the transaction, e.g., pollution (negative) or education (positive). (2) Public goods – non-excludable and non-rival, leading to free-rider problems, e.g., street lighting. (3) Information asymmetry – one party has more information than the other, e.g., second-hand car market (lemons problem). (4) Monopoly power – firms restrict output to raise prices, causing allocative inefficiency.

Q: What is the difference between normal profit and supernormal profit?

Normal profit is the minimum profit required to keep a firm in business in the long run; it is included as a cost (opportunity cost of entrepreneurship). Supernormal profit (or abnormal profit) is any profit above normal profit. In perfect competition, firms earn only normal profit in the long run due to entry and exit. In monopoly, firms can earn supernormal profit in the long run because of barriers to entry.

Q: How do I draw a diagram for a negative externality?

Draw a standard demand (private benefit) and supply (private cost) diagram. Then add a marginal social cost (MSC) curve above the supply curve, reflecting the external cost. The market equilibrium is where demand equals supply (private optimum). The social optimum is where demand equals MSC. The welfare loss is the triangle between the two equilibria. Show that output is higher than socially optimal, and price is lower.

Q: What is the significance of price elasticity of demand for a firm?

Price elasticity of demand (PED) tells a firm how responsive quantity demanded is to a price change. If demand is elastic (PED>1), a price decrease will increase total revenue, and a price increase will decrease total revenue. If demand is inelastic (PED<1), a price increase raises total revenue. Firms use this to set pricing strategies. For example, luxury goods often have elastic demand, while necessities like petrol have inelastic demand.

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Microeconomics explained

This topic covers the analysis of firm-level costs, revenues, and profits, including the distinction between short-run and long-run production, the law of diminishing returns, economies of scale, and the concept of profit maximisation.

What to demonstrate

Calculation of total, average, and marginal values for costs and revenues
Distinction between fixed and variable costs
Distinction between short run and long run

Show all 12 objectives

Explanation of the law of diminishing returns
Derivation of the long run average cost curve
Explanation of internal and external economies and diseconomies of scale
Profit maximisation condition (MR=MC)
Distinction between normal and abnormal profit
Distinction between accounting and economic profit
Understanding of internal and external growth of firms
Types of integration/mergers (horizontal, vertical, conglomerate)
Concepts of productive, allocative, and dynamic efficiency

Microeconomics exam tips

Topic Overview

Microeconomics is the branch of economics that studies the behaviour of individual economic agents—households, firms, and industries—and how they interact in markets. For WJEC A-Level Economics, this topic forms the foundation of understanding how prices are determined, how resources are allocated, and how decisions are made at the micro level. You'll explore concepts like supply and demand, elasticity, market structures (perfect competition, monopoly, oligopoly), and market failure. Mastering microeconomics is essential because it explains real-world phenomena such as why petrol prices fluctuate, how firms set prices, and why governments intervene in markets.

This topic is central to the WJEC specification, appearing in both the AS and A2 papers. At AS, you focus on basic demand and supply analysis, elasticity, and the concept of market equilibrium. At A2, you delve deeper into market structures, including cost and revenue curves, profit maximisation, and efficiency. You'll also examine market failures like externalities, public goods, and information asymmetries, and evaluate government policies to correct them. Understanding microeconomics not only helps you excel in exams but also equips you with analytical tools to critique economic policies and business strategies.

Microeconomics fits into the wider subject by providing the building blocks for macroeconomics. For instance, aggregate demand and supply are rooted in microeconomic concepts of individual demand and supply. Moreover, microeconomic principles underpin topics like international trade (comparative advantage) and development economics (market failures in developing countries). By studying microeconomics, you develop a rigorous, logical approach to problem-solving that is valued in economics degrees and careers in finance, consulting, and public policy.

Key Concepts

→Demand and Supply: The law of demand states that as price falls, quantity demanded rises (ceteris paribus), while the law of supply states that as price rises, quantity supplied rises. Market equilibrium occurs where quantity demanded equals quantity supplied.
→Elasticity: Price elasticity of demand (PED) measures responsiveness of quantity demanded to a change in price. PED = %ΔQd / %ΔP. If PED > 1, demand is elastic; if PED < 1, demand is inelastic. Income elasticity (YED) and cross-price elasticity (XED) are also crucial.
→Market Structures: Perfect competition features many firms, identical products, and no barriers to entry, leading to allocative and productive efficiency in the long run. Monopoly has one firm, high barriers, and can earn supernormal profits, leading to potential inefficiency. Oligopoly has few dominant firms with interdependence and strategic behaviour.
→Cost and Revenue Curves: Total cost (TC) = fixed cost (FC) + variable cost (VC). Average cost (AC) = TC/Q. Marginal cost (MC) = change in TC from producing one more unit. Revenue curves: total revenue (TR) = P×Q; average revenue (AR) = TR/Q = price; marginal revenue (MR) = change in TR from selling one more unit. Profit is maximised where MR = MC.
→Market Failure: Occurs when free markets lead to an inefficient allocation of resources. Examples include externalities (positive/negative), public goods (non-excludable and non-rival), and information asymmetry. Government intervention (taxes, subsidies, regulation) can correct market failure but may cause government failure.

Marking Points

Calculation of total, average, and marginal values for costs and revenues
Distinction between fixed and variable costs
Distinction between short run and long run
Explanation of the law of diminishing returns
Derivation of the long run average cost curve
Explanation of internal and external economies and diseconomies of scale
Profit maximisation condition (MR=MC)
Distinction between normal and abnormal profit
Distinction between accounting and economic profit
Understanding of internal and external growth of firms
Types of integration/mergers (horizontal, vertical, conglomerate)
Concepts of productive, allocative, and dynamic efficiency

Examiner Tips

💡Use appropriate diagrams to illustrate all cost and revenue concepts
💡Ensure you can calculate values for costs and revenues from provided data
💡Be prepared to evaluate the costs and benefits of firm growth and mergers
💡Clearly define efficiency types (productive, allocative, dynamic) when discussing firm performance
💡Always use precise diagrams: In WJEC exams, drawing accurate demand and supply curves, cost and revenue curves, and showing shifts (with arrows) is essential. Label axes, curves, and equilibrium points clearly. For market failure, illustrate externalities with MSC/MSB curves.
💡Evaluate with 'it depends': For higher marks, avoid one-sided arguments. When discussing government intervention, consider both benefits (e.g., reducing negative externalities) and drawbacks (e.g., government failure, unintended consequences). Use phrases like 'the extent to which...' and 'this depends on...'.
💡Master the definitions: Key terms like 'allocative efficiency', 'productive efficiency', 'normal profit', and 'supernormal profit' must be defined precisely. Use the exact wording from the specification. For example, 'allocative efficiency occurs when price equals marginal cost (P=MC).'

Common Mistakes

Confusing accounting profit with economic profit
Failing to distinguish between short-run and long-run cost structures
Misinterpreting the relationship between marginal product and marginal cost
Incorrectly identifying the profit-maximising output level
Confusing internal and external economies of scale
Misconception: 'A rise in demand always leads to a rise in price.' Correction: While a rightward shift in demand typically raises equilibrium price and quantity, the extent depends on the elasticity of supply. If supply is perfectly elastic, price remains constant.
Misconception: 'Monopolies are always bad for consumers.' Correction: Monopolies can lead to higher prices and lower output, but they may also benefit from economies of scale, leading to lower average costs. Natural monopolies (e.g., water supply) may be more efficient than competition.
Misconception: 'Price elasticity of demand is the same as the slope of the demand curve.' Correction: PED varies along a linear demand curve; it is not constant. At higher prices, demand is more elastic; at lower prices, it is more inelastic. The slope is only one factor.

Frequently Asked Questions

What is the difference between a movement along and a shift of the demand curve?

A movement along the demand curve occurs when the price of the good itself changes, leading to a change in quantity demanded (ceteris paribus). A shift of the demand curve happens when a non-price factor changes, such as income, tastes, or the price of related goods. For example, an increase in income shifts the demand curve for normal goods to the right, meaning at every price, consumers demand more.

How do I calculate profit maximisation output?

Profit is maximised where marginal revenue (MR) equals marginal cost (MC). In perfect competition, price equals MR, so the condition is P=MC. In imperfect competition, MR is less than price, so you find the output where MR=MC, then charge the price from the demand curve at that output. Remember to check that price is above average variable cost in the short run, otherwise the firm should shut down.

What are the main types of market failure?

The main types are: (1) Externalities – costs or benefits that affect third parties not involved in the transaction, e.g., pollution (negative) or education (positive). (2) Public goods – non-excludable and non-rival, leading to free-rider problems, e.g., street lighting. (3) Information asymmetry – one party has more information than the other, e.g., second-hand car market (lemons problem). (4) Monopoly power – firms restrict output to raise prices, causing allocative inefficiency.

What is the difference between normal profit and supernormal profit?

Normal profit is the minimum profit required to keep a firm in business in the long run; it is included as a cost (opportunity cost of entrepreneurship). Supernormal profit (or abnormal profit) is any profit above normal profit. In perfect competition, firms earn only normal profit in the long run due to entry and exit. In monopoly, firms can earn supernormal profit in the long run because of barriers to entry.

How do I draw a diagram for a negative externality?

Draw a standard demand (private benefit) and supply (private cost) diagram. Then add a marginal social cost (MSC) curve above the supply curve, reflecting the external cost. The market equilibrium is where demand equals supply (private optimum). The social optimum is where demand equals MSC. The welfare loss is the triangle between the two equilibria. Show that output is higher than socially optimal, and price is lower.

What is the significance of price elasticity of demand for a firm?

Price elasticity of demand (PED) tells a firm how responsive quantity demanded is to a price change. If demand is elastic (PED>1), a price decrease will increase total revenue, and a price increase will decrease total revenue. If demand is inelastic (PED<1), a price increase raises total revenue. Firms use this to set pricing strategies. For example, luxury goods often have elastic demand, while necessities like petrol have inelastic demand.

Microeconomics explained

What to demonstrate

Microeconomics exam tips

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