EECM2614: Microeconomics Course Notes

Microeconomics explains how individual economic agents—households, firms, and governments—make decisions when resources are scarce and alternatives exist. In EECM2614, the focus is on core microeconomic tools such as demand and supply, consumer choice, production and cost, competitive markets, and market power in various imperfectly competitive settings. These notes are tailored toward what South African students typically encounter in university and TVET microeconomics curricula, with emphasis on exam-ready definitions, diagrams described in words, worked examples, and application to policy and real-world markets in South Africa.

Section 1: Microeconomics Foundations (Choice, Scarcity, and Market Framework)

Microeconomics begins with the idea that decisions are made under scarcity, meaning not all wants can be satisfied at the same time. This forces trade-offs and opportunity cost. In examinations, you are often expected to connect theory (models and curves) to reasoning (why a curve shifts, how equilibrium changes, and what happens to price and quantity).

Scarcity, Choice, and Opportunity Cost

Opportunity cost is the value of the next best alternative forgone when a choice is made. For example, if a student spends time working part-time, the opportunity cost may include reduced study time (and possibly lower exam performance or fewer opportunities to learn). While this may feel “personal,” the same logic applies to production decisions by firms:

• If a firm uses workers for one task, the firm cannot use those workers for another task.
• If a firm uses a warehouse for storage, it cannot use the same space for production.

In microeconomic models:

• Households face trade-offs between consumption today and savings (which influences future consumption).
• Firms face trade-offs between using capital for machinery vs. expanding capacity or investing in technology.

Exam skill: When asked “why did the decision change?”, you must show the link between a change in incentives and a change in choices—often leading to a shift in demand, supply, or both.

The Basic Market Model: Demand, Supply, and Equilibrium

A common exam entry point is the market equilibrium framework.

• Demand reflects consumers’ willingness and ability to buy.
• Supply reflects producers’ willingness and ability to sell.

Equilibrium occurs at the price where:

• Quantity demanded = Quantity supplied.

Demand Law and Supply Law

The law of demand states: as price decreases, quantity demanded increases, ceteris paribus. The reason is usually explained via:

1. Substitution effect: consumers shift away from relatively expensive goods.
2. Income effect: lower prices increase real purchasing power (depending on whether the good is normal/inferior).

The law of supply states: as price increases, firms are willing to produce and sell more, ceteris paribus.

Distinguishing Movements vs Shifts

A major exam pitfall is confusing:

• Movement along a curve (caused by a change in price, holding other factors constant)
• Shift of a curve (caused by changes in determinants like income, tastes, costs, technology, taxes, etc.)

Demand Shifters (Non-Price Determinants)

Demand may increase (shift right) due to:

• Higher consumer income (for normal goods)
• Preferences/tastes change (e.g., advertising, trends)
• Higher prices of substitutes push consumers toward the good
• Lower prices of complements might increase demand
• Expectations of future price or income changes (if consumers expect higher future prices, they may buy more today)

Demand may decrease (shift left) due to:

• Lower income (especially for normal goods or if income falls significantly)
• Less favourable tastes
• Higher prices of complements (hurting joint consumption)

Supply Shifters (Non-Price Determinants)

Supply may increase due to:

• Lower input costs (e.g., cheaper electricity, raw materials)
• Better technology
• Lower taxes/subsidies (if the analysis assumes net effect makes supply cheaper)
• Fewer regulatory burdens or improved logistics
• Expectations of higher future prices: firms may restrict current supply if they expect higher prices later (this can also be modelled as a reduction in current supply)

Supply may decrease due to:

• Higher input costs (wages, fuel, capital costs)
• Disruptions (power outages affecting production, supply chain issues)
• Higher taxes
• New regulations increasing compliance costs

Worked Equilibrium Example (Conceptual)

Suppose a simplified market has:

• Demand: ( Q_d = 100 – 2P )
• Supply: ( Q_s = 20 + 3P )

Set (Q_d = Q_s):
[
100 – 2P = 20 + 3P
]
[
80 = 5P
\Rightarrow P = 16
]
Then:
[
Q = 100 – 2(16) = 68
]
So equilibrium price is 16 and equilibrium quantity is 68.

If the demand shifts right because income rises (increase willingness/ability to buy), equilibrium price and quantity typically rise (assuming supply stays unchanged). Exam questions often use this structure: identify the shift direction, then state the effect on equilibrium.

Market Outcomes and Welfare Intuition

Microeconomics connects markets to welfare:

• Buyers and sellers are both made better off by mutually beneficial trade.
• Efficiency and welfare measures depend on whether markets reflect true scarcity and costs.

Later sections will use elasticity and surplus ideas (consumer surplus, producer surplus) and analyse policy impacts like price ceilings, price floors, and taxes.

Microeconomics in the South African Context

South Africa’s markets are shaped by features often discussed in class:

• energy costs and reliability influencing production costs,
• transport/logistics costs affecting supply,
• high unemployment and income inequality affecting demand patterns,
• policy interventions such as taxes, tariffs, and regulation.

In exams, even if the question is theoretical, you may be asked to “apply” to local markets such as:

• bread and staple foods (supply interruptions),
• fuel and transport (input costs),
• private education and training (income and demand for skills).

The key is to keep your answers model-driven: explain how a policy or cost shock changes a determinant of demand or supply.

Section 2: Consumer Theory—Preferences, Utility, Demand, and Elasticity

Consumer theory studies how households choose consumption bundles. It is the foundation for deriving individual demand and understanding how consumers react to prices and income changes. Many EECM2614 exam questions test your ability to connect consumer preference assumptions to demand outcomes.

Utility and Preferences

A standard starting point is utility, which represents satisfaction from consuming goods. While utility is not directly observed, it helps model preferences.

Assumptions Used in Many Micro Courses

Common assumptions:

• Completeness: consumers can compare any two bundles (A preferred to B, or vice versa).
• Transitivity: if A is preferred to B and B to C, then A to C.
• Non-satiation: “more is better” (especially for goods that are not “free goods” in abundance).
• Diminishing marginal rate of substitution (for convex preferences), which implies decreasing willingness to trade away one good for another while retaining satisfaction.

Indifference Curves and Marginal Rate of Substitution (MRS)

An indifference curve shows combinations of two goods yielding the same utility. Points on the same curve are equally preferred.

• The curve typically slopes downward because to keep utility constant:
  • if you have more of Good X, you must have less of Good Y.
• Convexity to the origin implies that MRS decreases as consumption of Good X increases.

MRS (Marginal Rate of Substitution) is the rate at which consumers are willing to exchange Good Y for Good X while remaining on the same indifference curve.

At an optimum:

• MRS = Price ratio (in absolute terms), i.e.:
  [
  \text{MRS}_{XY} = \frac{P_X}{P_Y}
  ]

The Budget Constraint

A consumer with income (I) faces prices (P_X) and (P_Y). The budget line satisfies:
[
P_X X + P_Y Y = I
]

• Increasing income shifts the budget outward.
• Increasing price of X rotates the budget inward around the Y-intercept (and vice versa).
• Exam diagrams often require you to indicate which intercept changes and the direction of rotation.

Optimization and Corner vs Interior Solutions

A consumer chooses a bundle that:

• maximizes utility given the budget constraint.

There are two broad types of solutions:

1. Interior solution: optimum occurs where:
   • budget line is tangent to an indifference curve.
2. Corner solution: optimum occurs at a boundary (e.g., buy only one good), typically when preferences are perfect complements or when one good is strongly dominated.

Perfect substitutes often lead to corner choices at one extreme depending on which good has the lower price.
Perfect complements lead to fixed-proportion consumption (e.g., left shoes and right shoes).

Normal Goods, Inferior Goods, and Engel Curves

An Engel curve shows how quantity demanded changes with income.

• For normal goods, demand rises with income.
• For inferior goods, demand falls with income.

Example you might see in exam contexts:

• If income rises, consumers may shift from lower-quality transport to higher-quality options; the inferior good loses demand.

Deriving Individual Demand: From Choice to Demand

Demand can be derived from the consumer optimum as price changes. Conceptually:

• a change in price rotates the budget line,
• the tangency point (or corner solution) changes,
• the chosen quantity of the good changes.

This is the micro foundation for the demand curve: it summarises optimal quantities across different prices.

Price Changes and Substitution/Income Effects (Core Reasoning)

Many micro courses separate the impact of a price change into:

1. Substitution effect: consumer substitutes toward the relatively cheaper good.
2. Income effect: change in purchasing power due to price change.

For normal goods, both effects generally make demand move in the same direction (e.g., a price increase lowers demand).
For inferior goods, the income effect may partially offset the substitution effect.

Exam technique: If a question gives a good described as inferior and asks about response to a price increase, you must discuss whether the sign of income effect reverses.

Elasticity: The Link Between Theory and Policy

Elasticity measures responsiveness. It is central for analysing taxes, price controls, and welfare.

Types of Elasticity

1. Price elasticity of demand (PED):
   [
   E_d = \frac{dQ/Q}{dP/P}
   ]

• Often interpreted as % change in quantity demanded from a 1% change in price.
• If (|E_d| > 1): demand is elastic.
• If (|E_d| < 1): demand is inelastic.

2. Income elasticity of demand (YED):
   [
   E_y = \frac{dQ/Q}{dI/I}
   ]

• Positive for normal goods; negative for inferior goods.

3. Cross elasticity of demand (XED):
   [
   E_{xy} = \frac{dQ_x/Q_x}{dP_y/P_y}
   ]

• Positive for substitutes (when Py rises, demand for x increases).
• Negative for complements.

4. Price elasticity of supply (PES):
   Responsiveness of quantity supplied to price changes.

Determinants of Demand Elasticity

Demand tends to be more elastic when:

• there are many substitutes,
• the good is a luxury rather than a necessity,
• the consumer can easily postpone consumption,
• the time horizon is longer (more adjustment possible).

Demand tends to be less elastic when:

• the good is necessary and few substitutes exist,
• the consumer cannot adjust quickly,
• the good is habit-forming in a short timeframe.

Elasticity and Total Revenue

A widely tested result: the relationship between elasticity and total revenue (TR).

• If demand is elastic, a price increase reduces total revenue.
• If demand is inelastic, a price increase increases total revenue.
• If demand is unit elastic (elasticity = 1), total revenue stays constant with price changes.

Example with Numbers

Assume price rises from 10 to 12 (+20%). If quantity falls from 50 to 40 (-20%):

• Elasticity is -1 (in absolute value = 1),
• total revenue stays: initial TR = 10×50 = 500; final TR = 12×40 = 480 (not exactly equal due to rounding); with exact values you’d show TR stable.

In exams, if given clean numbers, show the TR effect clearly.

Worked Elasticity Reasoning for Exam Questions

Suppose:

• demand is price inelastic for electricity (in the short run),
• government increases electricity tariffs.

Short-run effects:

• quantity demanded drops only slightly,
• but expenditure (and producer revenue from selling electricity) may rise initially.

In the long run:

• consumers may invest in energy efficiency,
• demand may become more elastic.

This time horizon idea is crucial for exam responses about utilities.

Consumer Welfare: Consumer Surplus

Consumer surplus (CS) is area under the demand curve and above the price line (for linear demand in many exam problems). The intuition:

• consumers pay the market price,
• but many would have been willing to pay more.

When prices rise:

• CS decreases.

When taxes or price ceilings are introduced:

• CS may rise or fall depending on policy and whether supply/demand are distorted.

A typical exam question:

• “How does a tax affect consumer surplus and producer surplus?”
  You answer by describing deadweight loss and changes in quantities and prices.

Section 3: Production, Costs, and Competitive Markets (Efficiency and Profit Maximisation)

This section shifts from consumer-side behaviour to firm-side behaviour. Microeconomics courses usually emphasise how firms choose inputs and how cost structures determine supply decisions. In many EECM2614 exam questions, you must connect cost curves to market outcomes.

Production Functions and Marginal Productivity

A production function relates inputs to output. In a simple setup:

• (Q = f(L, K)) where L is labour and K is capital.

Important concepts:

• Marginal product of labour (MPL): additional output from one more unit of labour holding capital constant.
• Diminishing marginal returns: MPL eventually decreases when labour increases while other inputs are fixed (common in short-run analysis).

Worked Illustration

Imagine a short-run production where capital is fixed at a certain level. As labour increases:

• output rises at first,
• then labour additions become less productive,
• so output increases slower.

In exams, the qualitative shape is often enough:

• MPL increases → peaks → decreases.
• Total product rises at decreasing rates.

Short Run vs Long Run

Many cost concepts differ by time horizon.

• Short run: at least one input is fixed (e.g., capital stock).
• Long run: all inputs can vary (no fixed input).

This matters:

• short-run cost curves include fixed costs (e.g., rent, depreciation treated as sunk/fixed in that period),
• long-run cost curves represent expansion planning where the firm can re-optimise input choices.

Cost Concepts: Fixed, Variable, Average, Marginal

Let:

• Total Fixed Cost (TFC): cost that does not change with output in the short run.
• Total Variable Cost (TVC): cost that changes with output.

Then:
[
TC = TFC + TVC
]

Key averages:

• Average Fixed Cost (AFC): ( AFC = \frac{TFC}{Q} )
• Average Variable Cost (AVC): ( AVC = \frac{TVC}{Q} )
• Average Total Cost (ATC): ( ATC = \frac{TC}{Q} )

Marginal cost:
[
MC = \frac{dTC}{dQ} \quad \text{(or discrete change form)}
]

In many diagrams:

• MC crosses ATC and AVC at their minimum points (for smooth convex curves).

Example with Simple Numbers (Exam-Friendly)

Assume:

• TFC = 100 (constant).
  For outputs:
• Q=1, TVC=30 → TC=130 → ATC=130
• Q=2, TVC=50 → TC=150 → ATC=75
• Q=3, TVC=75 → TC=175 → ATC=58.33

Observe ATC falling initially because fixed costs spread out and variable costs rise slowly at first. Eventually, variable costs rise faster and ATC rises again.

Profit Maximisation in Perfect Competition

In perfect competition:

• firms are price takers (market price given),
• they face a perfectly elastic demand curve for their output at the market price.

The profit-maximising condition:

• produce where MR = MC.
  In perfect competition:
• MR = P, so:
  [
  P = MC
  ]
  provided output is where MC is rising and relevant.

Profit Calculation

Profit:
[
\pi = TR – TC = P\cdot Q – TC
]

• If (P > ATC): economic profit positive.
• If (P = ATC): zero economic profit.
• If (P < ATC) but (P \ge AVC): firm incurs losses but may continue short run because it covers variable costs.
• If (P < AVC): firm shuts down in short run.

Shutdown Rule and the AVC Minimum

Shutdown rule in short run:

• If price falls below AVC, producing yields lower profit than shutting down (since fixed costs still occur either way, the firm must at least cover variable costs).

Exam questions often ask you to identify:

• whether the firm shuts down,
• how profits change,
• how supply behaves.

Supply Curves from Cost Curves

For a competitive firm:

• in the short run, the firm’s supply curve is the part of MC above AVC minimum.
• In the long run, long-run supply incorporates entry/exit and the adjustment to zero economic profit.

Market Supply and Equilibrium

To analyse market-level outcomes:

• aggregate individual firm supply (add horizontally).

Then:

• equilibrium price and quantity determined by market demand and market supply.

If costs rise:

• supply shifts left/up,
• equilibrium price increases,
• quantity decreases.

In South Africa:

• if input costs rise (e.g., labour costs, fuel, electricity), market supply often decreases. Exam answers should highlight that supply depends on costs.

Economic Efficiency and Deadweight Loss

Microeconomics often evaluates outcomes using efficiency ideas:

• In perfect competition, if certain conditions hold, equilibrium can be efficient (no mutually beneficial trades left undone).
• Under taxes, price ceilings, or monopolies, distortions can create deadweight loss.

Even if the course notes don’t fully centre on welfare economics, you should connect:

• pricing mechanisms and marginal decisions (MC pricing) to efficiency.

Section 4: Market Power and Imperfect Competition (Monopoly, Oligopoly, and Strategic Behaviour)

Not all markets are perfectly competitive. When firms have market power, they can influence prices. Microeconomics studies how output and pricing decisions change as competition becomes imperfect.

Monopoly Basics: Barriers and Demand Face

A monopolist is the sole seller in a market with significant barriers to entry. Key properties:

• the monopolist faces the market demand curve,
• therefore the monopolist’s marginal revenue (MR) lies below price because selling more units requires lowering price for all units sold.

Exam diagram description:

• Demand curve slopes downward.
• MR lies below demand, typically steeper in linear demand cases.

Profit maximisation:

• choose output where (MR = MC),
• then determine price from demand at that output.

Monopoly Pricing and Deadweight Loss

Compared to competitive markets:

• monopoly output is lower,
• monopoly price is higher (if demand slopes downward normally).

Deadweight loss occurs because:

• some mutually beneficial trades that would happen under competition do not occur under monopoly output restriction.

Welfare Components

• Consumer surplus is reduced because consumers face higher prices.
• Producer surplus increases for the monopolist (profit can be positive).
• Total welfare typically falls due to deadweight loss.

Linear Demand Example (Precise)

Let demand be:
[
P = a – bQ
]
Then revenue:
[
TR = P\cdot Q = (a – bQ)Q = aQ – bQ^2
]
Marginal revenue:
[
MR = \frac{dTR}{dQ} = a – 2bQ
]
Set (MR = MC). If MC is constant at (c):
[
a – 2bQ = c \Rightarrow Q_m = \frac{a-c}{2b}
]
Price:
[
P_m = a – bQ_m = a – b\cdot \frac{a-c}{2b} = a – \frac{a-c}{2} = \frac{a+c}{2}
]

Under perfect competition with price equal to marginal cost (P=c):
[
Q_c = \frac{a-c}{b}
]
which is twice the monopoly quantity:
[
Q_c = 2Q_m
]
This clean relationship is often used in exam problems to demonstrate output reduction under monopoly.

Price Discrimination (Advanced but Often Tested Conceptually)

Price discrimination means the seller charges different prices to different consumers or groups, based on their willingness to pay.

Forms:

1. First-degree (perfect) discrimination: charges each consumer their maximum willingness-to-pay; can capture all consumer surplus.
2. Second-degree: different prices by quantity/versions (e.g., bulk discounts).
3. Third-degree: different prices to identifiable groups (e.g., students vs general public).

Requirements:

• firms must have market power,
• must be able to identify groups or separate markets,
• must prevent resale/arbitrage if third-degree discrimination.

Exam reasoning: Price discrimination can increase total welfare sometimes (if it allows the firm to sell to more consumers), but it depends on whether it reduces output restriction relative to standard monopoly.

Natural Monopoly and Regulation

A natural monopoly arises when:

• economies of scale are so strong that one firm can supply the whole market at lower average cost than multiple firms.

This is common in industries with:

• high fixed costs and large infrastructure networks (e.g., utilities).

Regulation might involve:

• price caps (target a “fair” price),
• cost-plus regulation (set price to cover costs plus margin; can lead to inefficiency if not monitored),
• aiming for MC pricing under constraints.

In exam questions, be careful:

• MC pricing may not cover average costs because average cost includes fixed costs; regulators may use two-part tariffs or subsidies.

Oligopoly and Strategic Interaction

Oligopoly features:

• few firms,
• significant strategic interdependence.

A classic framework is the Cournot model (quantity competition):

• each firm chooses quantity assuming the other’s quantity fixed,
• market price depends on total quantity.

Another is Bertrand model (price competition):

• firms choose prices assuming the other’s price fixed.

Key exam lesson:

• outcomes differ by model assumptions.
• Under Bertrand with homogeneous products and constant marginal costs, equilibrium can approach competitive results (price near marginal cost).

Collusion and Cartels

Firms might collude (implicitly or explicitly) to behave like a monopoly, increasing joint profits. However:

• collusion is unstable due to incentives to deviate.

In exam questions:

• you may be asked why cartels are difficult to maintain:
  • detection and enforcement,
  • incentives to cheat,
  • changing demand conditions.

Policy and Antitrust

Microeconomics links to competition policy:

• merger control,
• anti-cartel enforcement,
• assessing market concentration and barriers to entry.

South African students often encounter competition-related discussion in broader economics modules. In EECM2614, you should connect:

• market power effects (higher price, lower output)
• with regulation/antitrust rationale.

Section 5: Market Failures, Government Intervention, and Applied Elasticity/Welfare Analysis

Many microeconomics exams conclude with applications of theory to real policy problems: taxes, subsidies, price controls, and market failures like externalities and information asymmetry. Even if EECM2614 focuses strongly on standard topics, you should be able to apply elasticity and welfare reasoning.

Taxes: Who Really Bears the Burden?

A standard micro result: the incidence of a tax depends on relative elasticities of demand and supply.

• If demand is inelastic and supply elastic, consumers bear more of the tax (price rises a lot for them).
• If supply is inelastic and demand elastic, producers bear more (net price received falls a lot).

How to show in an exam:

1. Draw supply and demand.
2. Add tax as a wedge between what consumers pay and what producers receive.
3. Compare elasticities: steeper curves imply higher inelasticity.

Numerical Illustration

Suppose:

• demand and supply in linear form lead to equilibrium before tax.
  A tax shifts supply upward (or creates wedge).
  After tax:
• consumer price increases by some amount,
• producer price decreases by some amount.

Even without full algebra, you can:

• state the direction of price changes,
• attribute the magnitude to elasticity.

Subsidies and Their Effects

A subsidy reduces the effective cost for producers (shifts supply right or lowers wedge). Generally:

• equilibrium quantity increases,
• market price to consumers falls,
• but government pays the subsidy amount.

Subsidies can create welfare gains if they correct externalities (e.g., positive consumption externalities), but can also cause inefficiency if they distort signals without justification.

Price Ceilings and Price Floors

Price Ceiling (e.g., rent control, maximum prices)

If set below equilibrium:

• quantity demanded exceeds quantity supplied (shortage),
• rationing occurs through non-price mechanisms (queues, reduced quality, informal payments).

If set above equilibrium:

• it is non-binding and does nothing.

Price Floor (e.g., minimum wage, guaranteed prices)

If set above equilibrium:

• quantity supplied exceeds quantity demanded (surplus),
• unemployment or unsold output may occur depending on labour vs goods market.

For minimum wage in labour markets:

• the impact depends on labour market structure, presence of frictions, and elasticity of labour supply/demand.

In exam answers:

• always mention conditionality: “effects depend on elasticities and market conditions.”

Elasticity and Policy Effectiveness

Policy effectiveness often depends on elasticity.

Example: If government imposes a tax on a good with highly elastic demand (many substitutes), the quantity falls significantly, shrinking tax revenue and potentially increasing tax avoidance/substitution.

If demand is inelastic, quantity drops little, making the policy more revenue-generating but potentially more regressive (if poorer consumers spend a larger share of income).

South Africa’s taxation and affordability concerns often make this point in applied discussions:

• policies affecting staple goods or essential services can have disproportionate impacts on low-income households.

Externalities: When Markets Fail to Reflect True Costs or Benefits

An externality is a cost or benefit imposed on others without compensation.

• Negative externality (e.g., pollution): social cost > private cost → underproduction relative to social optimum.
• Positive externality (e.g., vaccinations): social benefit > private benefit → underconsumption relative to social optimum.

Externalities and Social Optimum

If a good creates negative externalities:

• the socially optimal output is lower than market output.
• policy like a tax equal to marginal external cost can internalise the externality.

If a good creates positive externalities:

• socially optimal output is higher.
• policy like a subsidy equal to marginal external benefit can internalise the externality.

Calculus-Free Exam Approach to Externalities

Even if your course uses diagrams more than algebra, use this structure:

1. Draw demand as marginal private benefit (MPB).
2. Draw supply as marginal private cost (MPC).
3. Social cost includes external costs; draw marginal social cost (MSC) above MPC.
4. Market equilibrium uses MPC and demand.
5. Social optimum uses MSC and demand.

Then:

• show divergence in quantity,
• show welfare loss due to externality.

Public Goods and the Free-Rider Problem

Public goods are:

• non-excludable and non-rival (e.g., street lighting in some contexts).
  In such markets, people have incentives to free-ride:
• they benefit without paying.

The market underprovides public goods relative to social optimum.

Policy options:

• government provision,
• taxes to fund provision,
• community-based funding schemes where feasible.

Information Asymmetry and Adverse Selection (Conceptual)

Microeconomics also addresses cases where buyers and sellers have different information.

In adverse selection:

• high-risk individuals might be more likely to buy insurance, raising insurer costs.
• this can lead to market unraveling.

Policy tools:

• regulation,
• mandatory insurance,
• signals and screening mechanisms.

Exams sometimes ask: “Give an example and explain the mechanism.” You can use examples relevant to South Africa such as:

• informal credit markets (information issues about borrowers),
• insurance markets (risk types and screening).

Keep answers focused on the causal chain:

• asymmetric information → wrong pricing → inefficiency.

Income Distribution, Fairness, and Efficiency Trade-Offs

Even in microeconomics, sometimes the exam question asks you to evaluate not only efficiency but also fairness.

• A market solution may be efficient but unequal.
• Government interventions might improve equity but can reduce efficiency.

In exam answers:

• state the trade-off clearly,
• mention that policy design tries to minimise the loss of efficiency while improving distribution.

Worked Policy Scenario with Elasticity and Welfare

Consider a policy response to reduce consumption of a harmful good (e.g., tobacco or alcohol taxes). You need to connect elasticity to welfare and fiscal outcomes.

1. Demand is often inelastic in the short run (habit formation).
2. Tax increases price; consumption falls but not drastically initially.
3. Government collects revenue.
4. Welfare changes include:
   • reduced negative externality consumption (benefit),
   • possible tax revenue recycling (if used for health services),
   • deadweight loss from reduced consumption below private optimum.

If the good has long-run elastic demand, consumption reduction is larger over time, potentially reducing deadweight loss more relative to benefits.

Summary of “Exam-Ready” Decision Rules

Across topics, you can apply consistent decision frameworks:

For Firms in Perfect Competition

1. Determine if the firm produces where (P=MC).
2. Check shutdown: if (P < AVC), shutdown.
3. Determine profit:
   • (P > ATC) profit,
   • (P = ATC) zero economic profit,
   • (P < ATC) losses.

For Monopoly

1. Find output where (MR=MC).
2. Use demand curve to get the monopoly price.
3. Compare with competition:
   • monopoly price higher, quantity lower,
   • deadweight loss exists.

For Elasticity-Based Policy

1. Identify whether demand or supply is more elastic.
2. Determine incidence direction:
   • more inelastic side bears more tax burden.
3. Anticipate quantity response:
   • more elastic → larger quantity change.

For Externalities

1. Negative externality → social cost curve above private cost.
2. Positive externality → social benefit curve above private benefit.
3. Use corrective policy (tax or subsidy) to internalise external effects.

Final Consolidation: Core Diagrams You Must Be Able to Describe Quickly

In many EECM2614 exams, diagrams are crucial even when not explicitly demanded. Practise describing them verbally with correct labels:

• Demand and Supply: downward demand, upward supply, equilibrium intersection.
• Demand shift vs movement: clarify what changes curve vs point.
• Indifference curves and budget line: tangency at optimum, slope equals price ratio.
• Cost curves: TFC horizontal, TVC rising, ATC/AVC U-shapes, MC intersects ATC and AVC minima.
• Competitive firm: price line horizontal at market price, intersect MC at output.
• Monopoly: demand and MR curves, output where MR=MC, then price from demand.
• Tax wedge: consumers pay higher price, producers receive lower, deadweight loss forms between new quantity and original.

Appendix: Quick Exam Practice Prompts (With Guidance)

These prompts mirror typical exam structures for EECM2614-style microeconomics:

1. Demand vs Supply Shift

   • Prompt: “Income increases; how does equilibrium change? What if the good is inferior?”
   • Guidance: state shift direction and effect; mention income elasticity sign.

2. Tax Incidence

   • Prompt: “Tax imposed on a good. If demand is perfectly elastic, who bears tax?”
   • Guidance: use elasticity logic; state incidence mainly falls on producers in perfect elasticity scenarios.

3. Shutdown Rule

   • Prompt: “Price falls below ATC but above AVC. Produce or shutdown?”
   • Guidance: produce in short run (losses) because AVC covered.

4. Monopoly Output

   • Prompt: “Explain why monopoly produces less than perfect competition.”
   • Guidance: MR below demand; firm chooses (MR=MC) leading to lower output; higher price.

5. Externalities

   • Prompt: “A factory pollutes a river. Explain market failure and a corrective policy.”
   • Guidance: negative externality; MSC above MPC; tax equal to marginal external cost internalises.

Closing Note on Consistency and Mastery

The strength of microeconomics is that it is coherent: the same logic—scarcity, incentives, marginal decision-making, and responsiveness—runs through consumer theory, producer theory, market outcomes, and welfare analysis. When answering EECM2614 exam questions, ensure your response follows the causal chain:

Change in a determinant → shift/movement → new equilibrium → welfare/profit implications → policy reasoning (if asked).