EKONOMIE 114: Principles of Microeconomics Study Guide

EKONOMIE 114 (Principles of Microeconomics) is a foundational course in how households and firms make decisions, how markets allocate scarce resources, and how government interventions change outcomes. This study guide focuses on the core microeconomic tools you must master—demand and supply, consumer choice, production and costs, perfect competition, market power, and government policy. It also gives South Africa–relevant contexts and exam-style reasoning so you can translate theory into answers.

1. Microeconomics Foundations and the Logic of Markets (Demand, Supply, and Elasticity)

Microeconomics studies individual economic units—consumers, firms, and particular markets—rather than the entire economy. The key question is: How do decisions at the individual level combine to determine prices, quantities, and welfare? You typically begin every exam problem by identifying a market, determining demand and supply, and then analyzing how a change (policy, income, technology, preferences) shifts curves and affects equilibrium.

1.1 The Microeconomic Problem: Scarcity, Choice, Incentives

At the heart of microeconomics is scarcity: resources are limited, so choices involve trade-offs. In exam questions, you often need to connect a change in incentives to a behavioral response. For example:

• If the price of bread rises, households substitute toward cheaper staples.
• If a firm receives a subsidy for green energy equipment, it changes production methods.
• If a government imposes a tax on cigarettes, consumers may reduce quantity demanded and shift toward untaxed brands or roll-your-own options.

Microeconomics is not only about “what happens,” but also about why it happens—through the model’s assumptions and incentive effects.

1.2 Demand: Meaning, Determinants, and the Demand Curve

Demand is the relationship between the price of a good and the quantity demanded, holding other factors constant.

Law of Demand (Core Exam Statement)

• As price falls, quantity demanded rises (and vice versa).
• The usual reasoning: substitution effect and income effect.

Determinants of Demand (Shifters)

When anything other than the good’s own price changes, demand shifts:

1. Income (I)
   • Normal goods: higher income → higher demand.
   • Inferior goods: higher income → lower demand.
2. Prices of related goods
   • Substitutes: higher price of substitute → higher demand.
   • Complements: higher price of complement → lower demand.
3. Preferences / tastes (including demographics and trends)
4. Expectations (future price changes)
5. Number of buyers (population and household formation)
6. Advertising and information

Demand Curve vs Demand (Typical Confusion)

• Along the demand curve: movement due to a change in own price.
• Shift in demand curve: movement due to other factors.

1.3 Supply: Meaning, Determinants, and the Supply Curve

Supply is the relationship between the price of a good and the quantity supplied, holding other factors constant.

Law of Supply

• As price rises, firms have stronger incentives to produce more → quantity supplied rises.

Determinants of Supply (Shifters)

1. Input prices (wages, raw materials, electricity)
2. Technology (productivity changes)
3. Taxes/subsidies (especially output or input taxes)
4. Number of firms / entry and exit
5. Expectations about future prices
6. Regulatory changes (safety standards, environmental restrictions)
7. Natural conditions (weather affects agriculture)

1.4 Market Equilibrium: Price and Quantity Determination

Equilibrium occurs where:

• Quantity demanded = quantity supplied

In most exam setups:

• You start with initial equilibrium at the intersection of demand and supply.
• Then you analyze what happens when one curve shifts.

Example (Exam-Style)

If demand for public transport rides increases due to higher commuting needs:

• Demand shifts right
• Equilibrium price rises and equilibrium quantity rises (assuming supply is not perfectly elastic/vertical).

If demand shifts left due to stronger remote work:

• Price falls, quantity decreases.

1.5 Comparative Statics: Analyzing Shifts Systematically

Comparative statics is about comparing one equilibrium to another after a change.

Use a disciplined step structure:

1. Identify the market (e.g., maize meal, taxi services, student accommodation).
2. Identify what changes (price, income, technology, taxes, expectations).
3. Decide whether it shifts demand or supply, and direction (right/left).
4. Predict changes in equilibrium price and quantity:
   • If demand increases: price ↑ and quantity ↑ (for standard downward demand and upward supply).
   • If supply decreases: price ↑ and quantity ↓.

Counter-Argument Potential (Common Exam Twist)

Sometimes the “change” you think affects demand actually affects supply (e.g., load shedding raises operating costs, so supply shifts left rather than demand shifting). Always examine whether the change affects buyers’ willingness to pay (demand) or sellers’ costs and ability to produce (supply).

1.6 Elasticity: The Sensitivity of Demand and Supply

Elasticity measures responsiveness. It is essential for policy analysis: the effect of taxes, price controls, and subsidies depends on elasticities.

Price Elasticity of Demand (PED)

[
PED = \frac{%\Delta Q_d}{%\Delta P}
]

• Typically negative, but we focus on magnitude (|PED|).
• More elastic: larger (|PED|) (buyers respond strongly to price changes).
• Less elastic: smaller (|PED|).

Key Factors Affecting PED

1. Availability of substitutes (many substitutes → more elastic)
2. Necessity vs luxury (necessities → less elastic)
3. Time horizon
   • Short run: more inelastic.
   • Long run: consumers and firms adjust more → more elastic.
4. Share of budget (bigger share → more elastic)
5. Definition of the market (narrowly defined goods → more elastic)

Income Elasticity of Demand (YED)

[
YED = \frac{%\Delta Q_d}{%\Delta Y}
]

• Normal goods: positive.
• Inferior goods: negative.
• Necessities: between 0 and 1 often (less income-sensitive).

Cross Elasticity (XED)

[
XED = \frac{%\Delta Q_{of\ good\ A}}{%\Delta P_{of\ good\ B}}
]

• Positive for substitutes.
• Negative for complements.

Price Elasticity of Supply (PES)

• Dependent on time to adjust and ability to change production.
• Often:
  • Short run: more inelastic supply (firms cannot rapidly alter capacity).
  • Long run: more elastic supply (firms can enter/exit and invest in capacity).

1.7 Using Elasticity in Exam Policies: Taxes, Subsidies, Price Floors, and Ceilings

Tax Incidence

A common misconception: “the party the government taxes pays the tax.” In reality, tax burden depends on elasticities.

• More inelastic side pays a larger share of tax.
• More elastic side pays a smaller share.

Example Logic (No Numerical Data Needed)

• If demand for a product is very inelastic (e.g., basic medication), consumers cannot easily reduce quantity, so they bear a large portion of any tax.
• If supply is relatively elastic, producers can adjust more; the supply side share becomes smaller.

Deadweight Loss (DWL)

When taxes distort prices and reduce quantity:

• Some mutually beneficial trades do not occur.
• Welfare losses beyond government revenue are DWL.

1.8 Worked Concept Example: Elasticity and a Subsidy to Renewable Energy

Suppose government subsidizes solar panel installation. This reduces the effective cost to consumers/households or installation firms.

• Demand may increase because consumers face lower price.
• Supply may also shift if firms invest in capacity and input purchasing.

Outcome predictions:

• Equilibrium quantity of solar installations rises.
• Price paid by consumers falls (or rises less).
• Government pays the subsidy, so welfare effects depend on:
  • Elasticities
  • Whether investment is long-term (future cost reductions)
  • Environmental externalities (addressed more formally later in the externalities section)

Elasticity will determine how much of the subsidy translates into higher quantities versus lower prices.

2. Consumer Behaviour and Demand Derivation (Utility, Budget Constraints, and Choice)

Consumer theory explains how individuals make choices under constraints, and it underpins demand relationships. Exams often test both the graphical intuition and the logical derivation of demand from preferences and constraints.

2.1 Utility and Preferences: The Vocabulary of Consumer Choice

Utility is a measure of satisfaction (ordinal—only ranking matters).

A typical assumption:

• Consumers can rank bundles based on preference.
• They prefer “higher” utility, meaning they choose the bundle they rank best.

In microeconomics you usually do not need to calculate exact “utility values” unless the exam explicitly uses numbers; you focus on ranking and choice.

2.2 Budget Constraint: The Consumer’s Feasible Set

If a consumer buys two goods—say X (e.g., airtime) and Y (e.g., data bundles)**—then the budget constraint is:

[
P_x X + P_y Y = M
]

Where:

• (P_x), (P_y) are prices
• (M) is income

Graph Interpretation

• Intercept on the X-axis: (M / P_x)
• Intercept on the Y-axis: (M / P_y)
• Slope: (-P_x / P_y)

A change in income shifts the budget line outward/inward (if both goods are normal). A change in prices rotates the line.

2.3 Indifference Curves: Preference Maps and Marginal Rate of Substitution

Indifference curves represent combinations of goods giving equal utility.

Properties (standard exam knowledge):

• Curves slope downward (more of one good requires less of the other to stay equally satisfied).
• Curves do not cross (consistent preferences).
• Often convex to the origin (diminishing marginal rate of substitution).

Marginal Rate of Substitution (MRS)

The MRS measures the rate at which a consumer is willing to trade Y for X while staying equally satisfied.

Graphically:

• (MRS) corresponds to the slope of the indifference curve (in absolute value terms).

2.4 The Choice Condition: Tangency and Optimization

The utility-maximizing bundle occurs where:

• The budget line is tangent to an indifference curve.

At tangency:
[
MRS = \frac{P_x}{P_y}
]

Meaning:

• The consumer’s willingness to trade equals the market’s trade-off.

2.5 Normal vs Inferior Goods: Income Effects

If a good is normal:

• When income increases, demand increases.

If the good is inferior:

• When income increases, demand decreases.

Indifference curve analysis can explain this via how the optimal consumption point moves when the budget line shifts outward.

2.6 Substitution Effect and Income Effect: The Total Response to a Price Change

When the price of a good changes:

• The consumer changes consumption due to:
  1. Substitution effect: relative price changes → substitution to the cheaper good.
  2. Income effect: real purchasing power changes.

Exam-Relevant Framing

• Substitution effect is usually negative for demand (higher price → lower quantity).
• Income effect can be negative for inferior goods, possibly offsetting substitution.

This is why an inferior good may exhibit unusual patterns (e.g., demand might increase when price rises in some ranges—though typically the demand curve slopes downward overall for standard models).

2.7 Revealed Preference and Practical Demand Reasoning

While many South African exam questions use graphs and formal consumer theory, some questions are more applied:

• If consumers buy more of a good when its price falls (holding income constant), revealed preference logic supports a downward demand relationship.

You can connect:

• Observed behaviour + comparative statics → demand curve reasoning.

2.8 Deriving Demand from Utility: From Individual Choice to Market Demand

To derive demand, you:

1. Determine the optimal bundle at each price level using tangency with budget constraint.
2. Record the quantity chosen of the good at each price.
3. That yields the demand curve.

For market demand:

• Add up individual demands horizontally (assuming independent consumers).
• Market demand depends on:
  • number of consumers
  • income distribution
  • preferences
  • availability of substitutes

2.9 Demand Curves and Elasticity: Linking Consumer Choice to Responsiveness

A central connection:

• Steeper indifference curves vs flatter ones influence how substitution affects choices.
• If consumers have many close substitutes and are willing to switch, demand becomes more elastic.

In exam answers, you can justify elasticity using:

• preference patterns (substitutability)
• constraints (time horizons)
• necessity status

2.10 South African Context Examples (Qualitative Integration)

Micro theory applies naturally to South African markets. Consider:

• Transport choices: If taxi fares rise, commuters may substitute toward buses or train services, depending on relative reliability and travel time. That is a substitution effect.
• Food budgeting: Income changes affect demand for staples like maize meal and rice differently depending on whether households treat them as normal goods or inferior substitutes.
• University students’ choices: If off-campus rent rises relative to residence fees, some students substitute toward residences (or share accommodation to reduce effective price per person).

In exams, you don’t need a perfect empirical statistic to apply microeconomics; you need correct directionality and reasoning.

3. Production, Costs, and Market Structures (From Firm Decisions to Competition and Power)

This section bridges micro theory with firm behaviour: firms convert inputs into outputs. You then analyze costs and how firms respond to prices under different market structures.

3.1 Production Function: Inputs, Output, and Efficiency

A production function links inputs to output:

• Labor (L), capital (K), technology (T)

In an exam definition:

• Output depends on the amount of inputs used and the technology level.

Law of Diminishing Marginal Returns

When you increase one input while holding others constant, at some point additional units create smaller increases in output.

This matters for:

• how marginal products behave
• how variable costs respond
• optimal choice of inputs later

3.2 Short Run vs Long Run: Why Time Matters

In microeconomics:

• Short run: at least one factor is fixed (e.g., factory size).
• Long run: all factors can vary (e.g., firms can change plant size).

Cost curves depend on this:

• Short-run average costs can decline and rise due to diminishing returns.
• Long-run average cost reflects optimal scaling and economies/diseconomies of scale.

3.3 Cost Concepts: Total, Average, and Marginal Costs

Let:

• Total Cost (TC) = Fixed Costs (FC) + Variable Costs (VC)
• FC does not change with output in the short run.
• VC changes with output.

Common cost curves:

• Average Cost (AC) = TC / Q
• Average Fixed Cost (AFC) = FC / Q
• Average Variable Cost (AVC) = VC / Q
• Marginal Cost (MC) = change in TC due to one more unit of output

Relationship Between AC and MC

• MC intersects AC at AC’s minimum.
• MC intersects AVC at AVC’s minimum.
• If MC < AC, AC falls; if MC > AC, AC rises.

This is often tested through graph interpretation.

3.4 Profit Maximization in Perfect Competition

In perfect competition, firms are price takers:

• the market sets the price
• the firm cannot influence it

A profit-maximizing firm produces where:
[
MR = MC
]
In perfect competition:

• (MR = P)

So:
[
P = MC
]
for the output level.

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

When Does a Firm Produce vs Shut Down?

A firm shuts down in the short run if it cannot cover variable costs:

• If (P < AVC), the firm produces zero in the short run.

If:

• (AVC \le P < AC): firm produces but earns losses (still may operate).
• (P \ge AC): firm earns normal or positive profits (depending on whether “normal profit” is included).

3.5 Supply of the Firm and Market Supply

Individual firm supply in the short run:

• MC curve above AVC.

To get market supply:

• Horizontal sum of individual firm supplies.

This directly links back to elasticity:

• Market supply depends on how many firms can enter/exit and how quickly production changes.

3.6 Monopoly and Market Power: Price Setting and Deadweight Loss

In monopoly, one firm is the sole seller. It faces the market demand curve directly, so it sets price/quantity strategically.

Key exam results:

• Monopoly chooses output where (MR = MC).
• Because of downward-sloping demand:
  • MR lies below P
• Monopoly produces less and charges more than in perfect competition.

Deadweight Loss (DWL)

Compared to efficient competitive outcomes:

• Monopoly creates DWL by restricting quantity.

Welfare decomposition in monopoly:

• Consumer surplus decreases
• Producer surplus increases partly
• Government revenue is not involved unless regulation/taxes occur
• DWL is lost surplus that would have occurred in mutually beneficial trades.

Price Discrimination (Advanced but Common)

If a monopoly can separate consumers into groups with different willingness to pay:

• It may capture more surplus
• Depending on type of discrimination and constraints, DWL can shrink.

However, conditions required for price discrimination matter:

• market power
• ability to prevent resale/arbitrage
• different elasticities across segments

3.7 Oligopoly and Strategic Interaction: Why “Interdependence” Matters

Oligopoly is characterized by a small number of firms and strategic behavior. Firms consider rivals’ reactions.

Classic exam anchors:

• game theory intuition
• reaction functions
• collusion vs competition

Even without full game theory calculations, you should:

• identify incentives to cheat on collusion
• show that unilateral deviations are profitable when agreements are not enforceable

3.8 Economies and Diseconomies of Scale

Cost advantages from scale:

• Economies of scale: average cost decreases as output increases.
• Diseconomies of scale: average cost increases at high output due to coordination complexity, bureaucracy, or inefficiency.

In exams, you may be asked:

• Why large firms may dominate
• Why entry might be difficult if incumbents have lower costs

This connects to monopoly/oligopoly barriers and regulatory policy.

3.9 South African Firm/Market Examples (Qualitative Integration)

You can apply these concepts to recognizable South African settings:

• Minibus taxi market (oligopolistic features and local market segmentation)
• Retail fuel markets (regulated or near-competitive at certain levels, but supplier constraints and transport costs matter for supply)
• Electricity generation and distribution (natural monopoly traits and high fixed costs)
• Agriculture and input supply (weather and input price changes shifting supply)

Exam answers typically need plausible micro logic, not exact empirical data.

4. Market Efficiency, Externalities, Public Policy, and Welfare Analysis

Now you connect the models to welfare outcomes and evaluate government interventions. This is where many learners lose marks because they provide definitions but not clear welfare implications.

4.1 Social Efficiency vs Market Outcomes

In perfect competition with no externalities and complete information:

• outcomes can be efficient (allocatively).

In the presence of externalities or market power:

• markets may produce too much or too little relative to the social optimum.

The welfare approach often involves:

• comparing private costs/benefits to social costs/benefits

4.2 Externalities: The Core Framework

An externality exists when the production or consumption of a good affects third parties without compensation.

• Negative externality: e.g., pollution
• Positive externality: e.g., vaccinations or education

The key difference is:

• private marginal cost (MPC) differs from social marginal cost (MSC)
• private marginal benefit (MPB) differs from social marginal benefit (MSB)

Negative Externality Example (Pollution)

If a factory pollutes air:

• Consumers/firms trading in the market ignore costs imposed on others.
• Market may produce more than socially optimal.

Policy goal:

• reduce output to social optimum by internalizing external costs.

4.3 Pigouvian Taxes and Subsidies

Pigouvian Tax

A government tax equal to the external cost per unit:

• shifts MPC up toward MSC
• moves equilibrium from market quantity (Q_m) toward social quantity (Q^*)

Tax impacts:

• raises price to reflect external costs
• reduces quantity
• generates government revenue (though not always directly equal to welfare loss)

Pigouvian Subsidy

For positive externalities:

• provide subsidy equal to the external benefit per unit
• encourages higher production/consumption

4.4 Cap-and-Trade and Regulation (Alternative Externality Policies)

For negative externalities, regulation can include:

• emissions standards (direct cap)
• cap-and-trade (market-based permit trading)

Key exam reasoning:

• If enforcement and compliance are realistic, these can reduce externalities.
• Welfare depends on:
  • cost of achieving reductions
  • uncertainty in abatement costs
  • administrative effectiveness

4.5 Public Goods and the Free-Rider Problem

A public good is:

• non-excludable
• non-rival

Example conceptually:

• certain public safety services
• national defense
• street lighting in some contexts (depending on metering and exclusion)

Because private firms cannot exclude non-payers:

• free riders occur
• market under-provision relative to social optimum

Policy:

• government provision or subsidies funded by taxes.

4.6 Information Asymmetry and Market Failure

When one party knows more than the other:

• adverse selection and moral hazard can occur.

• Adverse selection: wrong types enter market because risks are not recognized (common in insurance).

• Moral hazard: after contract, incentives change (e.g., insured parties take less care).

Possible policy tools:

• regulation
• disclosure requirements
• designing contracts with incentives
• insurance market structures.

Exams may present scenario-based questions; the correct approach is:

1. identify which side has information advantage
2. label the failure mechanism (adverse selection vs moral hazard)
3. propose policy consistent with incentive correction

4.7 Market Power and Welfare: Deadweight Loss and Transfers

When firms are monopolists (or have pricing power):

• inefficiency arises due to restricted quantity.
• DWL arises because fewer units are produced than in competitive equilibrium.

You also need to track transfers:

• from consumers to producers
• possibly to the government if taxes apply (but not necessarily)

4.8 Price Controls: Floors and Ceilings

Price Ceiling (e.g., rent ceiling)

• set below equilibrium price
• causes shortage (demand > supply)
• may cause waiting lists and rationing via non-price methods

Potential welfare arguments:

• improves affordability for those who receive goods
• harms efficiency and can reduce quality or investment incentives

Price Floor (e.g., minimum wage, agricultural price support)

• set above equilibrium price
• causes surplus (supply > demand)

In labour markets, minimum wages can:

• reduce employment if binding and if labour demand is elastic
• increase income for employed workers
• possibly improve living standards; welfare effect depends on employment and labour market conditions.

In exam answers, always indicate:

• whether the price control is binding
• which curve is affected relative to equilibrium

4.9 Cost-Benefit Analysis and Deadweight Loss

Common welfare decomposition used in exams:

• Consumer surplus (CS)
• Producer surplus (PS)
• Government revenue (if taxes)
• Deadweight loss (DWL)

A tax typically:

• increases wedge between buyers’ and sellers’ prices
• reduces quantity
• creates DWL because trades with high marginal value to buyers but low marginal value to sellers (or vice versa) stop.

4.10 South African Policy-Relevant Applications

Many South African exam contexts relate to:

• environmental regulation (air quality, water use)
• public health externalities
• education and skill development as positive externalities
• infrastructure as public goods or quasi-public goods

In answering policy questions, it is enough to show:

• you understand why markets might fail
• what policy instruments correct those failures
• how to predict direction of quantity and welfare outcomes

No detailed government budget numbers are required unless the exam gives them.

5. Exam Problem-Solving Skills: Step-by-Step Methods, Common Pitfalls, and Integrated Practice Scenarios

This final section is practical: how to structure answers for maximum marks in EKONOMIE 114. It includes methods for solving typical curve problems and evaluating market outcomes using elasticity, consumer choice reasoning, firm cost logic, and welfare analysis.

5.1 The “Mark-Optimized” Exam Answer Structure

When faced with a question, use a consistent structure.

For Demand/Supply/Elasticity Problems

1. State the type of change: own price vs shifters.
2. Draw or describe the correct shift: demand/supply right/left.
3. Predict direction of:
   • price change
   • quantity change
4. Mention elasticity if taxes/subsidies/price controls are involved:
   • who bears the burden
   • magnitude implications
5. Add welfare outcomes if asked:
   • DWL
   • CS/PS changes

For Consumer Theory Problems

1. Identify the good(s) and the variable change (income or price).
2. Determine whether it shifts the budget line or changes the slope.
3. Explain substitution effect direction.
4. Explain income effect direction given whether good is normal/inferior.
5. Conclude total change in quantity demanded.

For Firm/Course Problems

1. Identify market structure (perfect competition, monopoly, oligopoly).
2. Provide the profit-maximization condition:
   • competitive: (P = MC)
   • monopoly: (MR = MC)
3. Use cost relationships:
   • shutdown condition: (P < AVC)
   • profitability: compare (P) to (AC)
4. Draw the result conceptually or describe output/price.

For Externalities/Policy Problems

1. Determine sign of externality.
2. Distinguish private vs social marginal conditions.
3. Provide the correction instrument:
   • tax for negative externalities
   • subsidy for positive externalities
   • regulation/cap-and-trade where asked
4. State welfare outcome:
   • increased quantity or decreased quantity
   • reduced DWL
   • distributional effects as appropriate

5.2 Common Pitfalls and How to Avoid Them

Pitfall 1: Confusing Movement Along vs Shift of Curves

• Movement along demand: own price changes.
• Shift of demand: income/preferences/related prices/expectations/number of buyers changes.

Pitfall 2: Saying “Tax goes to government” without incidence reasoning

Taxes create incidence determined by elasticities, not just by who is legally taxed.

Pitfall 3: Using Monopoly comparisons incorrectly

If monopoly power exists:

• monopoly price is higher than competitive price
• monopoly quantity is lower than competitive quantity

Pitfall 4: Ignoring shutdown rules

In perfect competition:

• production decisions depend on AVC coverage.

Pitfall 5: Misinterpreting externality direction

• Negative externality → produce too much (relative to social optimum)
• Positive externality → produce too little (relative to social optimum)

5.3 Integrated Practice Scenario A: Subsidy, Elasticity, and Market Outcomes

Scenario: Assume a government introduces a subsidy for LPG (liquefied petroleum gas) cylinder refills to help households with energy costs. Suppose the subsidy reduces the effective price consumers pay.

Step 1: Identify the change

• Consumers face a lower price → demand increases (move to a new equilibrium along supply, plus possible shift depending on expectations).
• Producers may also respond by adjusting supply, but first analysis often treats supply as unchanged unless input costs or technology change.

Step 2: Predict equilibrium outcomes

• Quantity increases
• Price faced by consumers falls relative to pre-subsidy price
• Price net of subsidy for producers may differ from the consumer price

Step 3: Use elasticity to explain magnitude

If demand is:

• inelastic: quantity increases modestly; much of subsidy translates into lower consumer prices.
• elastic: quantity increases strongly; subsidy encourages substantial additional consumption.

Step 4: Welfare analysis

• Government revenue decreases due to subsidy spending.
• Consumer surplus likely increases.
• Producer surplus may increase depending on pass-through.
• Deadweight loss depends on whether subsidy causes overconsumption relative to any externality context.

If LPG substitution also reduces harmful biomass burning (a positive externality such as improved air quality), a subsidy could be welfare-enhancing. If not, it might simply transfer resources.

5.4 Integrated Practice Scenario B: Negative Externality from a Factory and Policy Choice

Scenario: A manufacturing plant releases emissions that reduce air quality for nearby residents. The market for the factory’s output is competitive, and the market price reflects only private costs.

Step 1: Determine externality sign

• Emissions harm third parties → negative externality.

Step 2: Compare marginal private and social costs

• (MPC < MSC)
• Social optimum occurs at a lower quantity where (MSC = MSB) (in a simplified single-market framework).

Step 3: Predict market outcome without policy

• Market equilibrium quantity is greater than social optimum.
• Overproduction creates deadweight loss.

Step 4: Choose policy

• Pigouvian tax on emissions per unit:
  • pushes firms to reduce output
  • aligns private incentives with social costs
• Cap-and-trade:
  • sets emissions quantity constraint
  • relies on market trading to achieve reductions efficiently

Step 5: Incidence and efficiency notes

Tax incidence depends on elasticities of demand and supply in the output market and possibly on responsiveness of emission abatement.

In an exam, you do not need all computations unless provided. You do need clear logic and direction.

5.5 Integrated Practice Scenario C: Minimum Wage, Labour Demand Elasticity, and Welfare

Scenario: A government sets a minimum wage above the equilibrium wage. Employers are deciding how many workers to hire.

Step 1: Identify price floor binding?

• Minimum wage above equilibrium → binding.

Step 2: Predict labour market outcome

• Quantity of labour demanded (employment) decreases.
• Quantity of labour supplied (job seekers) increases.
• Unemployment rises (shortage of jobs, surplus labour supply).

Step 3: Elasticity connection

• If labour demand is more elastic:
  • employment reduction is larger.
• If labour demand is inelastic:
  • employment reduction is smaller.
• If labour supply is elastic:
  • increased unemployment can be larger.

Step 4: Distribution and welfare

Welfare evaluation is ambiguous without numbers:

• employed workers: higher wages (transfer from firms)
• unemployed workers: reduced employment
• possible productivity and efficiency effects (e.g., higher wages attract better workers or reduce turnover), which can partially offset welfare losses.

In exam answers, you should highlight both sides: distributional gains vs potential efficiency and employment losses.

5.6 Integrated Practice Scenario D: Monopoly Pricing and Deadweight Loss

Scenario: A monopolist in a local service market sets price to maximize profit. Demand is downward sloping.

Step 1: Mark the monopoly condition

• Monopoly chooses output where (MR = MC).

Step 2: Compare to competition

• In perfect competition:
  • (P = MC) and equilibrium yields higher quantity.
• Under monopoly:
  • price higher, quantity lower.

Step 3: Welfare decomposition

• Consumer surplus decreases.
• Producer surplus increases (but not necessarily enough to offset consumer loss).
• Deadweight loss arises from reduced trades.

Step 4: Regulation possibilities

• Price caps can move monopoly outcome closer to competitive equilibrium.
• However, price caps may cause investment or quality problems if set too low (incentives matter).
• Taxes on monopoly profits or demand-side regulation can also affect outcomes.

5.7 Quantitative Skills: Using Elasticity with Numbers (Template Method)

When a question gives numbers, use a structured method.

Given

• Price changes from (P_1) to (P_2)
• Quantity changes from (Q_1) to (Q_2)

Use percentage change

[
%\Delta P = \frac{P_2-P_1}{P_1}\times 100
\quad;\quad
%\Delta Q = \frac{Q_2-Q_1}{Q_1}\times 100
]

Then:
[
PED = \frac{%\Delta Q}{%\Delta P}
]

Interpret

• (|PED|>1): elastic
• (|PED|<1): inelastic
• (|PED|=1): unit elastic

For elasticity-based incidence:

• more inelastic side bears more of tax burden.

5.8 Graph Skills: What Examiners Expect You to Do

In many EKONOMIE 114 exam scripts, the graph is evaluated for correctness and reasoning. Common graph expectations:

1. Draw axes clearly and label them (Price on vertical, Quantity on horizontal for market graphs).
2. Label demand (D) and supply (S).
3. Show initial equilibrium and new equilibrium points.
4. Indicate welfare areas (CS, PS) and/or deadweight loss triangles if asked.
5. For consumer graphs, label budget line and indifference curves, mark tangency point.

Even if you do not have time for a perfect drawing, correctness in direction and labeling can still earn marks.

5.9 Rapid Review Checklist (Last-Minute Revision)

Use this checklist to ensure you can recall exam-critical concepts quickly.

Demand and Supply

• Own price → movement along curve; other factors → shifts
• Equilibrium where Qd = Qs
• Predict direction of price and quantity changes

Elasticity

• PED formula and interpretation
• Key factors: substitutes, necessity, time horizon, budget share
• Tax incidence: inelastic side pays more

Consumer Theory

• Utility maximization: tangency (MRS = price ratio)
• Normal vs inferior goods and income effect direction
• Substitution effect and income effect after price change

Firms and Costs

• Profit maximization:
  • Perfect competition: P = MC
  • Monopoly: MR = MC
• Shutdown: if P < AVC produce nothing in short run
• Relationship: MC intersects AC at AC minimum

Market Failure and Policy

• Negative externality: overproduction; positive externality: underproduction
• Pigouvian tax/subsidy aligns private with social incentives
• DWL arises from distortions
• Price controls can cause shortages/surpluses

Cluster Summary Notes (Institution-Focused Approach)

EKONOMIE 114 is often assessed across South African institutions with similar microeconomic foundations but sometimes different emphasis (graphs vs calculations vs case-based reasoning). Use the methods above to adapt to exam styles commonly found in universities, colleges, and TVETs.

How to adapt across South African learning contexts

• If your syllabus emphasizes diagrams, practise clean curve-shift and welfare diagrams.
• If your syllabus emphasizes calculations, practise elasticity with percentage-change computations and simple incidence reasoning.
• If your syllabus uses case studies, practise “identify the mechanism” (demand vs supply; private vs social marginal effects; competition vs monopoly; elasticity implications).

If your lecturer provides a particular case study (e.g., transport fares, food price inflation, energy subsidy, pollution control), the micro framework in Sections 1–4 remains the backbone—your job is to map the case details to the correct model component and then produce a logically consistent direction-of-change answer with welfare implications where required.