ECO105D: Economics I Exam Notes

Economics I (commonly coded like ECO105D in some South African universities and TVET/college-linked pathways) is the foundation course where you learn how to reason like an economist: how markets allocate scarce resources, how incentives shape behaviour, and how macroeconomic aggregates (like inflation and unemployment) respond to policies. These exam notes consolidate the core microeconomic and macroeconomic tools that typically appear in tests and final assessments—especially in South African curricula that align with mainstream Economics I content.

The guide is written to be exam-ready: clear definitions, diagrams described in words, step-by-step problem-solving methods, and typical question patterns with worked-style examples.

Section 1: Core Economic Concepts, Scarcity, Choice, and Basic Tools

Economics is often defined as the study of how people and societies make choices under scarcity. Scarcity exists because resources are limited (time, labour, capital, natural resources) while wants are extensive. The central question becomes: what should be produced, how should it be produced, and for whom should it be produced?

1.1 Scarcity, Opportunity Cost, and Economic Thinking

Scarcity does not only mean “having no resources.” It also means that resources are not unlimited, so choices have trade-offs. When you choose one option, you give up another. That “given up” value is the opportunity cost.

Opportunity cost (exam emphasis)

• If you spend time studying, the opportunity cost might be a job shift you could have worked.
• If a government spends money on infrastructure, the opportunity cost might be reduced spending on education.

Key exam habit: Always express opportunity cost in terms of next best alternative.

Example (micro)

A student has R200 to spend on either:

• groceries that last two weeks, or
• a textbook that improves performance but costs a term.

If they choose the textbook, the opportunity cost is the groceries they could have purchased (and the benefit they would have received from them).

1.2 Positive vs Normative Statements

Economics distinguishes between:

• Positive statements: describe “what is” (e.g., “An increase in the petrol price reduces demand for petrol”).
• Normative statements: prescribe “what ought to be” (e.g., “The government should reduce petrol taxes”).

In exams, you may be asked to classify statements. Use this rule:

• If it uses “should,” “must,” “ought,” “best,” “good/bad” → likely normative.
• If it uses facts and predictions without moral judgement → likely positive.

1.3 Production Possibilities Frontier (PPF)

A PPF shows combinations of two goods an economy can produce using all resources efficiently. It typically curves outward due to increasing opportunity costs.

Common PPF diagram features:

• Inside the frontier: inefficient/underutilised resources (unemployment, idle factories).
• On the frontier: efficient production.
• Outside the frontier: currently unattainable (would require more resources or better technology).

Law of increasing opportunity cost

As production shifts from one good to another, opportunity cost rises—reflected by the PPF becoming more bowed.

Exam-style question types

1. “If the economy moves from point A to point B, what happens to opportunity cost?”
2. “How does technology improvement affect the PPF?”
   • It shifts outwards (higher capacity).
3. “How does unemployment affect the PPF?”
   • It may not shift frontier, but moves the economy inside it.

1.4 Demand, Supply, and Market Equilibrium Foundations

Economics I often starts micro topics with basic supply and demand.

Demand (D)

Demand refers to the relationship between price and quantity demanded, holding other factors constant.

Law of demand: as price increases, quantity demanded decreases (typically downward-sloping demand curve).

Factors that shift demand:

• income (normal vs inferior goods)
• tastes/preferences
• prices of related goods (substitutes/complements)
• expectations (future prices)
• number of buyers

Supply (S)

Supply refers to the relationship between price and quantity supplied.

Law of supply: as price increases, quantity supplied increases (typically upward-sloping supply curve).

Factors that shift supply:

• production costs (wages, raw materials)
• technology
• taxes/subsidies
• expectations
• number of sellers

Equilibrium

Market equilibrium is where:

• quantity demanded = quantity supplied
• the price has no tendency to change (given assumptions)

Exam concept: “movement along” vs “shift”

• Movement along the curve: due to a change in the good’s own price.
• Shift of the curve: due to non-price factors (income, costs, etc.).

1.5 Elasticity: Sensitivity to Change

Elasticity measures how responsive quantity demanded or supplied is to changes in price or income.

Price elasticity of demand (PED)

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

• If |PED| > 1: elastic demand (quantity responds strongly).
• If |PED| < 1: inelastic demand (quantity responds weakly).
• If |PED| = 1: unit elastic.

Factors affecting PED

• availability of substitutes
• necessity vs luxury
• time horizon (long run tends to be more elastic)
• share of income spent on the good

Exam-friendly elasticity application

• If demand is inelastic, a tax increases prices to consumers and reduces quantity less drastically.
• If demand is elastic, consumers can avoid the tax by reducing quantity or switching to substitutes.

Revenue test (often used)

Total revenue (TR) effects of price changes:

• If demand elastic → raising price lowers TR.
• If demand inelastic → raising price increases TR.
• If unit elastic → TR unchanged.

1.6 Cost Concepts: Fixed, Variable, Total, Marginal

Even if your exam leans conceptual, cost calculations appear frequently in Economics I.

• Fixed cost (FC): does not vary with output in the short run.
• Variable cost (VC): changes with output.
• Total cost (TC) = FC + VC
• Average cost (AC) = TC/Q
• Marginal cost (MC): cost of producing one more unit.
  [
  MC = \Delta TC / \Delta Q
  ]

Typical exam interpretation

• MC tends to cut through AC and AVC at their minimum points (graph intuition).
• If MC < AC, AC falls as output increases; if MC > AC, AC rises.

1.7 Utility, Preferences, and Indifference Curves (if included in your course)

Some Economics I courses include basic consumer theory:

• Utility: a measure of satisfaction.
• Budget constraint: combinations of goods a consumer can afford.
• Indifference curves: show bundles with equal utility.

Marginal rate of substitution (MRS) is the rate at which consumers trade one good for another while maintaining the same utility level.

Exam concept: where the highest attainable indifference curve touches the budget line is the optimum consumption point (assuming standard convexity).

Why this matters

It connects to demand behaviour: changes in relative prices rotate the budget line, shifting the chosen bundle.

1.8 Linking Concepts into “Economist Mode”

To do well in exams you must link topics:

• Scarcity → choice → opportunity cost
• Choice under incentives → demand/supply responses
• Elasticity → how much behaviour changes
• Costs → how firms choose output and pricing (even at intro level)
• Equilibrium → consistent interaction of buyers and sellers

Section 2: Microeconomics Essentials — Consumers, Firms, Markets, and Policy Effects

This section deepens the microeconomics toolkit: how markets form prices, how consumers and firms behave, and how interventions (taxes, subsidies, price floors/ceilings) change outcomes.

2.1 Consumer Choice and Demand Derivation (Intro-Level)

Even when you do not formally derive Marshallian demand, exams often test understanding of:

• the budget constraint
• preference direction
• how optimum changes when prices or income change

Budget line logic

If income is M and prices are (P_x) and (P_y), the budget constraint is:
[
P_x x + P_y y = M
]

• The slope of the budget line depends on relative prices: (-P_x/P_y).
• A price increase for one good makes that good “more expensive,” rotating the budget line inward.

Income effect and substitution effect (common question)

• Income effect: change in consumption due to real purchasing power changing.
• Substitution effect: change due to relative price changes.

For normal goods:

• Income effect reinforces higher quantity when income increases.
  For inferior goods:
• Income effect works against the normal direction.

2.2 Market Structures: Perfect Competition vs Monopoly (Conceptual)

Economics I often includes a comparison of:

• perfect competition
• monopoly (and sometimes monopolistic competition/oligopoly as extensions)

Perfect competition (core assumptions)

• many buyers and sellers
• homogeneous product
• perfect information (in simple versions)
• firms are price takers
• entry and exit are easy

Implication: each firm takes the market price as given.

Monopoly

• single seller in the market
• barriers to entry (legal, technical, control of resources)
• price setter (has market power)

Implication: monopoly faces a downward-sloping demand curve and chooses quantity strategically.

Exam comparisons you should be able to state

• monopoly typically leads to higher prices and lower quantities than competition (in standard models)
• monopoly can produce deadweight loss due to reduced trade beyond social optimum

2.3 Government Intervention: Taxes, Subsidies, and Their Incidence

Taxes and subsidies are frequently assessed through:

• shifts in supply/demand
• new equilibrium
• tax incidence (who actually pays)

Specific tax (ad valorem not always required in intro)

Suppose a per-unit tax is imposed on producers:

• supply shifts upward by the tax amount (in a simplified model).
• new equilibrium has:
  • lower quantity
  • price paid by consumers higher than price received by producers

Tax incidence depends on elasticities:

• more inelastic side bears more of the tax.

Key statement for exams: The side with less elastic demand/supply pays a larger share of the tax.

2.4 Price Ceilings and Price Floors

Price ceiling (e.g., rent control, maximum price)

• set below equilibrium price
• leads to shortage if binding

Consequences:

• excess demand (queue, rationing)
• may reduce quality or supply incentives
• black markets may arise

Price floor (e.g., minimum wage, minimum price for agricultural products)

• set above equilibrium price
• leads to surplus if binding

Consequences:

• excess supply
• need for government buybacks or support measures
• can reduce employment if minimum wage exceeds equilibrium and labour markets are sensitive

Important nuance: labour markets can behave differently if there are institutional frictions or monopsony power, but intro Economics I often asks the basic “surplus/shortage” reasoning.

2.5 Externalities and Market Failure

Externalities cause divergence between private and social costs/benefits.

• Negative externality (e.g., pollution): the firm’s private cost is lower than the social cost.
• Positive externality (e.g., vaccinations): benefits spill over to others.

Negative externality in simple terms

Market equilibrium occurs where private marginal cost equals demand, but socially optimal output is lower where social marginal cost equals demand.

Policy tools:

• corrective taxes (Pigouvian taxes)
• regulation/standards
• tradable permits (cap-and-trade)
• subsidies for positive externalities

2.6 Public Goods and Free-Riding

Public goods have:

• non-excludability: hard to prevent use
• non-rivalry: one person’s consumption does not reduce others’ benefit

Because people may free-ride, markets may underprovide public goods.

Examples often discussed:

• national defence
• street lighting
• clean air (also externalities)

Policy response:

• government provision
• compulsory contributions or taxation mechanisms

2.7 Risk, Asymmetric Information, and Intro Market Failure

Some Economics I courses briefly address:

• adverse selection (when buyers know more than sellers)
• moral hazard (after insurance is purchased, behaviour changes)

Exam questions may ask:

• how information problems distort markets
• why regulation or standard contracts may help

2.8 Worked Problem Pattern: Tax and Elasticity (Sample-Style)

A common exam problem gives:

• a demand function and supply function
• a per-unit tax
• asks for new equilibrium prices/quantity
• asks who pays what share

Even if your course doesn’t require algebraic derivation, you must articulate the chain of logic.

Procedure outline:

1. Write equilibrium without tax: (Q_d(P) = Q_s(P)).
2. Apply tax:
   • if producers pay: buyers pay (P_c), producers receive (P_p = P_c – t).
3. Substitute into demand and supply to solve for (Q).
4. Calculate:
   • (P_c)
   • (P_p)
5. Determine incidence:
   • tax burden on consumers = (P_c – P^*) or share via price change
   • burden on producers = (P^* – P_p)

Where (P^*) is original equilibrium price.

2.9 Policy Evaluation: Efficiency, Equity, and Costs

Economics tests increasingly ask for multi-criteria evaluation:

• efficiency: does policy improve total surplus?
• equity: who benefits and who bears costs?
• administrative feasibility: can it be implemented?
• incentive effects: will policy change behaviour as intended?

Example: subsidy vs tax for a desired outcome

• Subsidy to encourage renewable energy may increase adoption (efficiency gains if externality exists), but could be costly to taxpayers.
• Tax on pollution improves incentives, but may raise production costs and shift burdens unevenly if firms pass costs to consumers.

2.10 Micro Summary Skills Checklist (Exam Readiness)

When you see a question about markets:

• Identify whether the question is about movement along curves or shifts
• Identify the direction of change:
  • tax → supply shift up (if on producers)
  • subsidy → supply shift down
  • demand shifter: income, preferences, substitute price
• Apply elasticity to determine incidence and welfare effects
• Mention efficiency loss (deadweight loss) for distortions

Section 3: Macroeconomics Essentials — GDP, Inflation, Unemployment, Money, and Aggregate Demand/ Supply

Economics I usually includes a macro module that covers measurement of the economy and how business cycles and policy relate to inflation and unemployment.

3.1 GDP and National Income Accounting (Measurement)

Gross Domestic Product (GDP) measures the value of goods and services produced within a country during a period.

Three approaches to GDP (exam-friendly)

1. Expenditure approach:
   [
   GDP = C + I + G + (X – M)
   ]
   where:
   • (C) = consumption
   • (I) = investment
   • (G) = government spending
   • (X – M) = net exports
2. Income approach: sums income earned by factors of production.
3. Production approach: sums value added across industries.

Key exam nuance: GDP counts production, not ownership transfer. Some transactions are excluded because they don’t represent new production (e.g., existing asset sales).

Example (numbers)

If:

• (C = 800)
• (I = 200)
• (G = 150)
• (X = 120)
• (M = 180)

Then:
[
GDP = 800 + 200 + 150 + (120 – 180) = 800 + 200 + 150 – 60 = 1{,}090
]

3.2 Real vs Nominal Variables; Price Indices

Nominal GDP measures output using current prices. Real GDP adjusts for inflation.

Deflators and index logic

Common indices:

• CPI (Consumer Price Index): tracks consumer prices.
• GDP deflator: adjusts overall domestic output prices.

If nominal GDP grows faster than real GDP, inflation may be driving the difference.

Exam question pattern:

• “Given a base year and current prices, compute the index.”
• “Given CPI, compute inflation rate.”

Inflation rate calculation:
[
\text{Inflation rate} = \frac{CPI_{t} – CPI_{t-1}}{CPI_{t-1}} \times 100%
]

3.3 Unemployment: Types and Measurement

Unemployment is not a single uniform concept. Often you see:

• frictional unemployment: people between jobs
• structural unemployment: mismatch of skills/locations
• cyclical unemployment: due to downturns in aggregate demand

Some exams incorporate the labour force:

• labour force = employed + unemployed
• unemployment rate = unemployed / labour force

Labour force participation rate (sometimes)

[
\text{LFPR} = \frac{\text{Labour force}}{\text{Working-age population}}
]
A lower participation rate can hide unemployment pressures.

3.4 Aggregate Demand (AD) and Aggregate Supply (AS)

A basic macro diagram:

• AD: downward sloping due to wealth/interest-rate channels (depending on model).
• SRAS: upward sloping in the short run; LRAS: vertical at potential output in many models.

Potential output

Potential output is sustainable output based on resources and technology. When actual GDP differs, the economy faces output gaps and inflation pressure.

3.5 Keynesian Cross and Demand Shocks (Short-Run Reasoning)

In simpler versions:

• Consumption depends on income.
• Investment depends on interest rates and expectations.
• Government affects aggregate demand through (G).
• Net exports depend on exchange rates and external demand.

A positive demand shock shifts AD right:

• output rises in the short run
• inflation rises (depending on model/horizon)

A negative demand shock shifts AD left:

• output falls
• inflation declines

3.6 Inflation: Causes and Policy Implications

Inflation can be driven by:

• demand-pull (AD increases)
• cost-push (higher production costs, e.g., wages, fuel)
• expectations and persistence (people adjust pricing behaviour)

In a typical Economics I exam, you often need to identify:

• which shock would shift AD or AS
• what policy would counter it (monetary contraction vs fiscal adjustments)

3.7 Monetary Policy Basics: Interest Rates, Money Supply, and Transmission

Monetary policy often operates through:

• central bank controlling interest rates or influencing money supply
• affecting borrowing costs
• impacting consumption and investment
• influencing aggregate demand
• affecting inflation

Interest rate channel:

• higher interest rates → lower investment and consumption of credit
• lower AD → reduced inflation pressure

Exam “explain the chain” requirement:
You should not just say “tighten monetary policy reduces inflation.” You must explain the transmission mechanism.

3.8 Fiscal Policy: Government Spending and Taxation

Fiscal policy affects:

• aggregate demand directly through government spending (G)
• disposable income through taxes → changes consumption (C)
• long-run growth effects if spending is targeted to productivity (in extended curricula)

Common fiscal policy types:

• expansionary fiscal policy: increase (G) or reduce taxes
• contractionary fiscal policy: reduce (G) or raise taxes

Possible exam nuance: fiscal policy can be limited by:

• crowding out (if interest rates adjust)
• debt sustainability concerns
• implementation lags

3.9 Business Cycles: Recession, Recovery, and Stabilisation

In macro, economies fluctuate:

• expansions: rising output, often lower unemployment
• recessions: falling output, rising unemployment
• stabilisation attempts: monetary and fiscal policies to reduce volatility

Even if the class doesn’t require full time-series, you should interpret:

• output gap sign (+ or -)
• inflation trend direction
• unemployment trend direction

3.10 Monetary-Fiscal Mix and Trade-offs

A common exam prompt:

• “If inflation is high and unemployment is also high, what should policy do?”

Standard logic:

• high inflation → contractionary monetary policy (lower AD)
• high unemployment → expansionary fiscal policy (raise AD)

But if both apply simultaneously, policy requires balancing and may prefer the policy that targets the dominant cause (supply shock vs demand shock).

Section 4: South African Context — Interpreting Economics I Through Local Data, Institutions, and Policy Themes

This section grounds the concepts in South Africa-relevant examples. It does not assume you must know every latest statistic, but it teaches you how to interpret typical exam-style South African policy narratives using macro and micro logic.

4.1 South African Labour Market and Unemployment Reasoning

South Africa frequently appears in economics exams because unemployment and inequality are persistent macro concerns.

How to use unemployment theory to answer SA questions

If a question asks why unemployment remains high, you should consider:

1. Structural factors
   • skills mismatch
   • sectoral shifts
   • location mismatch (job opportunities concentrated in specific regions)
2. Frictional factors
   • job search processes
3. Cyclical factors
   • insufficient aggregate demand
4. Institutional factors
   • minimum wage effects (simplified reasoning)
   • collective bargaining structures
   • informality and labour market segmentation

What exams usually want in your explanation

• connect theory to mechanisms
• avoid single-cause explanations
• show that different unemployment types require different remedies

For example:

• structural unemployment → training and labour market matching
• cyclical unemployment → macro stabilisation and demand support

4.2 Inflation, Cost Pressures, and Exchange Rates

South Africa’s inflation dynamics can be shaped by:

• food and fuel costs (cost-push)
• exchange rate movements affecting import prices
• monetary policy credibility and inflation expectations

How to interpret “inflation rises”

In a typical exam answer, you should identify the likely source:

• If international commodity prices rise → cost-push → AS shifts left/up
• If domestic demand surges → demand-pull → AD shifts right

Then state policy response:

• demand-pull: monetary tightening/AD reduction
• cost-push: may require supply-side actions and careful monetary response

4.3 Fiscal Policy and Government Spending Choices

When exam questions discuss fiscal policy in South Africa, they usually test whether you can:

• explain how fiscal changes shift AD
• evaluate effectiveness and limitations
• discuss public spending priorities

Example reasoning pattern

If government increases infrastructure spending:

• (G) rises → AD increases → short-run output rises
• could raise future productivity if spending improves capacity

But limitations:

• implementation lags (policy effects not instant)
• debt and interest costs
• potential inefficiencies

4.4 Taxes, Subsidies, and Redistribution

South Africa’s welfare and tax policy debates often revolve around:

• social grants (income support)
• tax reforms
• VAT and excise duties

Economics I logic:

• taxes affect prices and purchasing power
• subsidies can correct externalities or support affordability
• redistribution affects consumption patterns, demand composition, and inequality

If the question asks about incidence

Use elasticity:

• For goods with few substitutes (inelastic demand), taxes shift more to consumers.
• For labour or commodities with more flexibility, incidence may shift differently.

4.5 Market Failure Themes Relevant to South Africa

In exam essays and short answers, you might be asked about:

• pollution and environmental regulation
• under-provision of public goods
• information asymmetry in credit markets
• corruption and governance failures (used as a proxy for inefficiency)

How to structure an answer on market failure

A good template:

1. Define the market failure type (externality, public goods, imperfect information).
2. Explain the mechanism of inefficiency (private vs social incentives).
3. Identify the consequence (deadweight loss, underproduction, quality problems).
4. Propose a policy remedy.
5. Mention limitations/trade-offs.

4.6 Using Diagrams in South African Policy Questions (Without Getting Penalised)

Even if the exam is textual, diagrams may give points. Because South Africa is often used in scenario questions, you can mention:

• AD-AS shift diagrams
• supply and demand shifts
• unemployment and inflation interpretations via macro diagrams

Typical exam instruction: “Explain using a diagram.”
A safe approach is to describe:

• “AD shifts right because…”
• “AS shifts left due to higher input prices…”
• “Equilibrium moves to… output and price level changes…”

4.7 Case Logic: Drought/Load Shedding/Food Prices (General Mechanism)

South Africa sometimes faces shocks affecting agriculture and electricity supply. In Economics I logic:

• higher input costs for firms → AS shifts left
• supply constraints reduce output → unemployment pressures can rise if demand doesn’t adjust
• consumer prices rise → inflation pressure

Policy responses in theory:

• short-run: stabilisation to prevent demand collapse
• medium-run: supply-side investments and efficiency improvements

Even if the exam doesn’t require factual dates or numbers, it rewards correct mechanism-based reasoning.

4.8 Growth and Investment: Interpreting “I” in (GDP = C + I + G + (X – M))

Investment (I) is crucial. In South African context, exam questions may link investment to:

• interest rates
• investor confidence
• policy uncertainty
• infrastructure reliability

Economics I logic:

• higher interest rates reduce investment
• infrastructure constraints reduce expected returns
• policy certainty can lower risk premium and encourage investment

4.9 External Sector: Net Exports and Exchange Rate Pass-Through

If the exchange rate depreciates:

• import prices rise → inflation increases
• exports become cheaper to foreigners → export demand may increase
• but output depends on whether the supply side can expand

In exam answers, emphasize:

• exchange rate effect on AD via net exports
• cost-push effect on AS due to import prices

4.10 Building High-Scoring South African Exam Answers

A high-scoring answer tends to include:

• correct model identification (AD/AS vs supply/demand vs externalities)
• mechanism explanation (what shifts, why)
• policy evaluation (who wins/loses; trade-offs)
• policy link back to objectives (employment, inflation, growth, poverty reduction)

This section prepares you to “translate” South African economic headlines into Economics I reasoning, which is the skill many students find hardest under exam pressure.

Section 5: Exam Preparation Strategy — Problem-Solving, Common Question Types, Diagrams, and Guided Practice

This final section is deliberately exam-focused: it gives you repeatable methods for calculations, structured essay writing, diagram answering, and handling uncertainty in multi-part questions.

5.1 How Economics I Questions Are Typically Structured

You will commonly encounter:

• define/explain short questions (2–5 marks)
• diagram questions (5–10 marks)
• calculation questions (numerical supply/demand, GDP, elasticity, unemployment rate)
• multi-part scenarios that require connecting micro and macro logic
• essay questions (15–25 marks) on market failure, policy evaluation, or macro stabilisation

Exam strategy principle: Always allocate your time based on marks. In multi-part questions, ensure each part is answered distinctly—even if answers overlap.

5.2 Diagram Method: “Label, Shift, Equilibrium, Consequences”

When a question asks for a diagram, use this consistent approach:

1. Draw axes and identify whether it’s price-quantity (micro) or price level-output (macro).
2. Label curves (D, S; or AD, AS).
3. State shift direction:
   • “Demand increases: D shifts right.”
4. Show new intersection and label new equilibrium points.
5. Explain effects:
   • price increases/decreases
   • quantity increases/decreases
6. Add welfare/policy if asked:
   • taxes create deadweight loss
   • price ceilings create shortages
   • externalities cause under/overproduction

Common mark-grabbers

• correctly naming movement vs shift
• labeling the new equilibrium
• stating “other things equal” assumptions

5.3 Numerical GDP and Index Practice (Step-by-Step)

GDP expenditure calculation

If given values for (C, I, G, X, M), compute:
[
GDP = C + I + G + (X – M)
]
Then, if asked about growth:
[
\text{Real growth} \approx \frac{RGDP_t – RGDP_{t-1}}{RGDP_{t-1}} \times 100%
]

Inflation using CPI

If:

• CPI in 2022 = 120
• CPI in 2023 = 132

Then inflation:
[
\frac{132-120}{120} \times 100% = 10%
]

Exams may also ask for:

• interpret inflation meaning
• effects on purchasing power

5.4 Elasticity Calculations and Interpretation

Elasticity from two points

If quantity changes from (Q_1) to (Q_2) as price changes from (P_1) to (P_2):
[
PED = \frac{(Q_2 – Q_1)/Q_{avg}}{(P_2 – P_1)/P_{avg}}
]
where (Q_{avg}) and (P_{avg}) are averages (depends on course convention).

If you’re allowed simpler method:
[
PED \approx \frac{%\Delta Q}{%\Delta P}
]

Interpretation rule: always conclude elasticity type and explain behaviour implication (pass-through, revenue effect).

5.5 Tax Incidence and Welfare Concepts (How to Answer Incidence Questions)

A typical incidence question:

• “A tax of t is imposed. Show the effects and determine who bears it.”

Your answer should include:

1. supply shift (if tax on producers) or demand shift (if tax on consumers)
2. new equilibrium:
   • consumer price rises by some amount
   • producer price falls by some amount
3. incidence:
   • consumers pay difference between consumer price and pre-tax price
   • producers pay difference between pre-tax price and producer price
4. mention deadweight loss if marks allow

Efficiency interpretation (often asked)

• taxes can reduce equilibrium quantity below socially optimal due to distortion of incentives

5.6 Short Essay Writing Framework: Market Failure and Policy

For essay topics like:

• externalities and corrective policy
• public goods and provision
• market failures in general and how policy remedies work

Use a structured argument:

1. Define the market failure (2–3 sentences).
2. Explain the mechanism:
   • private vs social costs/benefits
3. Show inefficiency:
   • under/overproduction in a basic model
4. Propose policy instruments:
   • taxes/subsidies, regulation, permits
5. Evaluate trade-offs:
   • administrative costs, distortions, equity concerns
6. Conclude with link to objectives

5.7 Macro Essay Framework: AD-AS Stabilisation and Trade-offs

For macro questions like:

• inflation and unemployment
• policy trade-offs
• demand shocks vs supply shocks

Use:

1. Identify the macro problem:
   • high inflation? high unemployment?
2. Determine likely source:
   • AD shock or AS shock
3. Show diagram shift(s) described verbally or drawn
4. Recommend policy:
   • monetary/fiscal/supply-side
5. Explain trade-offs:
   • unemployment-fighting vs inflation control
6. Conclude with a coherent policy mix

5.8 Guided Practice: Multi-Part Question Templates (With Answer Skeletons)

Below are “templates” you can adapt during revision. The point is to practice the exam logic, not only memorize definitions.

Template A: “Explain the effect of an increase in petrol prices”

Answer should include:

1. Micro: petrol is a good; price increase reduces quantity demanded (movement along D).
2. Related goods: substitutes like public transport may increase demand.
3. Elasticity: if long-run elasticity higher, demand falls more over time.
4. Policy: if taxes are involved, discuss incidence.
5. Macro link:
   • fuel is an input → cost-push → AS shifts left → inflation.
   • lower economic activity may affect unemployment.

Template B: “Why might unemployment remain high?”

1. classify unemployment:
   • structural, frictional, cyclical
2. link to labour market:
   • skill mismatch, weak demand
3. propose solutions:
   • training and labour matching (structural)
   • stabilization measures (cyclical)
4. evaluate limitations:
   • policies take time; informality complicates measurement

Template C: “Assess whether government should subsidise education”

1. identify externalities:
   • education yields social benefits (positive externalities)
2. explain market outcome:
   • private benefits lower than social benefits → underconsumption
3. policy:
   • subsidy, loans, scholarships
4. trade-offs:
   • fiscal cost, targeting challenges
5. conclusion:
   • support is justified if externalities and equity concerns are significant

5.9 Revision Plan and How to Study for Maximum Marks

A practical revision schedule (generic) that suits Economics I:

• Week 1: Micro foundations (demand/supply, elasticity, basic consumer/producer ideas)
• Week 2: Micro failures and policy (externalities, public goods, taxes/subsidies)
• Week 3: Macro basics (GDP, unemployment, inflation, AD-AS)
• Week 4: Integration + diagrams + past-question practice

Even without exact dates, the principle is to build from foundations to policy evaluation and then practise exam-style application.

5.10 Common Mistakes That Lose Marks

1. Confusing shift vs movement
   Example: “tax increases price → supply curve shifts” is correct logic only if the tax changes supply position; otherwise if price changes due to other factors, you may only need movement along curves.
2. Misclassifying normative vs positive
   “Government should reduce inflation” is normative, not a factual claim.
3. Incomplete diagram labeling
   Missing axis labels or unlabeled curves can reduce marks.
4. No mechanism explanation
   Saying “AD decreases so output decreases” without stating why AD decreases usually loses reasoning marks.
5. Elasticsearch of definitions without application
   Exams reward application to the specific scenario given.

5.11 Final Exam Mindset: Clarity Under Pressure

When you read the question:

1. Underline the key variables (price? output? employment? CPI? tax?).
2. Decide which model applies:
   • supply/demand, AD-AS, elasticity, unemployment identity
3. Choose the direction:
   • “increase in X causes Y to rise/fall” with a mechanism.
4. Produce the answer with:
   • definitions + diagrams + policy logic + trade-offs (if asked)

This discipline is often what differentiates top grades from average performance.

South African Institution Integration Note (Course Coding and Exam Fit)

ECO105D is used across different institutional offerings, but the underlying skills tested in Economics I remain strongly aligned with standard Economics I outcomes: market equilibrium reasoning, elasticity, cost and producer basics, macro measurement (GDP/CPI), unemployment and inflation logic, AD-AS dynamics, and policy evaluation. The approach in these notes—definitions plus diagrams plus mechanism explanations—matches how South African universities and TVET curricula commonly structure assessments: scenario-based questions, short diagram prompts, and essays that demand coherent application to local policy themes.

Conclusion (Study Summary)

Economics I is fundamentally about model-based reasoning. You learn to translate real-world statements into the language of economics—scarcity and opportunity cost, supply/demand and equilibrium, elasticity and incidence, market failure and policy remedies, and macro aggregates like GDP, inflation, and unemployment with AD-AS dynamics. If you revise using the structured methods above (shift vs movement, mechanism chains, consistent diagrams, and multi-part answer templates), you will be equipped for the most common question patterns in ECO105D-style Economics I exams across South African institutions.