ECON201: Intermediate Microeconomics and Applications Course Notes (South Africa)

Intermediate Microeconomics and Applications (commonly coded ECON201 in South African universities) builds the analytical tools you need to understand how households, firms, and markets make decisions. These notes focus on the core theory—demand, supply, consumer choice, producer choice, and equilibrium—then connect it to real policy and application contexts typical of South Africa’s exam and tutorial styles. The emphasis is on exam-ready problem-solving, intuitive economic reasoning, and consistent use of models such as elasticities, utility maximization, cost minimization, market equilibrium, externalities, and imperfect competition.

Section 1: Foundations, Demand and Elasticity in Practice (ECON201 Core)

Microeconomics in ECON201 typically starts by asking: how do we model choices when preferences and constraints exist? Before deeper optimization, you must be fluent with market demand and supply, and—crucially—elasticity, because elasticity links theory to measurement and policy impacts.

1.1 Supply, Demand, and Competitive Equilibrium

A competitive market model typically assumes:

Many buyers and sellers
Firms are price takers
No individual agent can influence the market price

Let market demand be Q_d(P) and market supply be Q_s(P). Equilibrium occurs when:

Q_d(P*) = Q_s(P*)
The equilibrium price is P* and equilibrium quantity is Q*

In exam problems, you are often asked to find:

Demand and supply equations (or intercepts) from graphs or given data
Equilibrium by solving simultaneous equations
Comparative statics: how equilibrium changes after a tax/subsidy, shift in demand, etc.

Example (numerical competitive equilibrium):
Suppose a market has:

Q_d = 120 − 2P
Q_s = 20 + 3P

Set Q_d = Q_s:

120 − 2P = 20 + 3P
100 = 5P
P* = 20
Then quantity:
Q* = 120 − 2(20) = 120 − 40 = 80

So equilibrium is (P*, Q*) = (20, 80).

Comparative statics you should master

When demand shifts right (increasing demand at each price), P* increases and Q* increases. When supply shifts right, P* falls while Q* rises. A common exam twist is to ask about tax incidence even when the supply and demand curves are not symmetric.

1.2 Elasticity: The Bridge Between Theory and Outcomes

Elasticity measures responsiveness of quantity to changes in determinants (typically price). You should be comfortable with:

Price elasticity of demand (PED)
Price elasticity of supply (PES)
Cross-price elasticity
Income elasticity
Elasticity of substitution (later in consumer/production)

Point elasticity vs arc elasticity

Point elasticity uses calculus at a specific point.
Arc elasticity uses average values across an interval (often required when only discrete price-quantity pairs are given).

Arc PED formula (common in exam questions):
If price changes from P1 to P2 and quantity from Q1 to Q2:
[
\text{PED} = \frac{(Q_2 – Q_1)/\left(\frac{Q_1+Q_2}{2}\right)}{(P_2 – P_1)/\left(\frac{P_1+P_2}{2}\right)}
]
Often you take absolute values or interpret signs consistently (demand is typically negative elasticity).

Relationship between elasticity and total expenditure

A classic rule:

If PED is elastic (|PED| > 1), price increases reduce total revenue (expenditure).
If PED is inelastic (|PED| < 1), price increases raise total revenue.

Why this matters for policy: In South Africa, exam questions often contextualize how VAT or excise taxes affect affordability and government revenue. Even if you don’t know real tax rates, the model logic is tested: the revenue outcome depends on elasticity.

1.3 Elasticity with Linear Demand Curves

If demand is linear:
[
Q = a – bP
]
Then elasticity varies along the curve. For linear demand:

Elasticity is more elastic near the upper end (close to the choke price).
Elasticity is less elastic near the lower end.

Exam method: compute PED at the relevant equilibrium point, not just a generic statement.

Example:
Let Q = 100 − 5P. At P = 10:

Q = 100 − 50 = 50
Slope: dQ/dP = −5
Point elasticity:
[
\text{PED} = \frac{dQ}{dP}\cdot\frac{P}{Q} = (-5)\cdot\frac{10}{50} = -1
]
So at this point, demand is unit elastic.

1.4 Determinants of Demand Elasticity (What to Write in Essays)

When asked to explain elasticity determinants, you want a crisp economics response:

Availability of substitutes: More substitutes → more elastic demand.
Necessities vs luxuries: Necessities → more inelastic.
Time horizon: Long-run demand tends to be more elastic because consumers can adjust (move, switch, install alternatives).
Share of income spent: Higher share → greater sensitivity → more elastic demand.
Definition of the market: Narrow definition (e.g., “instant noodles” vs “food”) increases substitutability → more elastic.

South Africa application angle:
Many essential goods face lower demand elasticity (e.g., basic food items). Luxury or branded categories often have higher elasticity because alternatives are easier to switch to. In exam scenarios, if a tax is imposed on a good with high PED, quantity falls sharply, and the tax revenue outcome can be smaller than predicted by naive intuition.

1.5 Worked Tax Incidence and Elasticity

A standard ECON201 topic is: who bears the tax burden? Even if the tax is collected from consumers or producers, the burden depends on relative elasticities.

General principle:

More inelastic side bears a larger share of the tax.
If demand is more inelastic than supply, consumers bear more.
If supply is more inelastic than demand, producers bear more.

Numerical illustration:
Assume:

Demand: Q = 100 − 2P
Supply: Q = 20 + P
Find equilibrium without tax:
Set 100 − 2P = 20 + P
80 = 3P → P* = 26.667
Q* = 100 − 2(26.667) = 46.667

Now impose a per-unit tax t = 10. Model as:

Consumers face price Pc
Producers receive price Pp = Pc − t
Demand uses Pc, supply uses Pp.

Let:

Demand: Q = 100 − 2Pc
Supply: Q = 20 + (Pc − 10)

Set equal:
100 − 2Pc = 20 + Pc − 10
100 − 2Pc = 10 + Pc
90 = 3Pc
Pc = 30
Then Pp = Pc − 10 = 20
Quantity:
Q = 100 − 2(30) = 40

Now tax burden:

Consumers’ price rises from 26.667 to 30: increase 3.333
Producers’ price falls from 26.667 to 20: fall 6.667
So producers bear more because supply is relatively more inelastic in this setup.

How to write it: show both price changes and interpret using elasticity logic.

1.6 Cross-Price and Income Elasticity: Substitutes and Complements

Cross-price elasticity:
[
E_{xy} = \frac{%\Delta Q_x}{%\Delta P_y}
]
Interpretation:

Positive → substitutes
Negative → complements
Zero → independent

Income elasticity:
[
E_I = \frac{%\Delta Q}{%\Delta Y}
]
Interpretation:

> 0 normal good
> 1 luxury
0 < E_I < 1 necessity (positive but inelastic to income)
< 0 inferior good

These measures often appear in applications where the question asks you to categorize goods (e.g., transport vs fuel categories, or formal vs informal services).

Section 2: Consumer Choice, Utility Maximization, and Demand Estimation

After mastering supply/demand mechanics, ECON201 typically moves to microfoundations: how preferences and constraints produce demand. You should be comfortable moving between:

Utility maximization and demand
Budget constraints and optimal bundles
Lagrangian methods
Slutsky equation / substitution and income effects (often later, but you should recognize structure)

2.1 Preferences and Indifference Curves

Preferences are represented by utility functions or indifference maps. Key properties:

Completeness: any two bundles can be compared
Transitivity: if A preferred to B and B to C, then A to C
Non-satiation: more is better (except some specialized cases)
Diminishing marginal rate of substitution (MRS): typical for convex indifference curves

Indifference curve facts (write clearly):

Downward sloping when more of one good means less of another.
Higher utility curves are preferred to lower ones if preferences are monotonic.

Convexity implies:

Consumers prefer diversified bundles.
The MRS diminishes as you consume more of one good.

2.2 Budget Constraint and Opportunity Cost

With goods x and y, prices p_x and p_y, income m:
[
p_x x + p_y y \le m
]
Budget line:
[
p_x x + p_y y = m
]

Intercepts: x-intercept = m/p_x, y-intercept = m/p_y
Slope: −p_x/p_y (opportunity cost of x in terms of y)

2.3 Utility Maximization and Lagrangean Setup

A general approach:

Write utility u(x, y)
Set up Lagrangian:
[
\mathcal{L} = u(x,y) + \lambda (m – p_x x – p_y y)
]
First-order conditions:

∂L/∂x = 0
∂L/∂y = 0
∂L/∂λ = 0 (budget binds at optimum for standard goods)

Solve for x*, y*

Example with Cobb–Douglas

Let:
[
u(x,y) = x^{0.5} y^{0.5}
]
Prices p_x = 2, p_y = 1, income m = 100.

For Cobb–Douglas, optimal shares are constant:

Spend fraction 0.5 of income on each good.

Thus:

Expenditure on x: 0.5m = 50 → p_xx = 50 → 2x = 50 → x = 25
Expenditure on y: 0.5m = 50 → 1y = 50 → y = 50

So optimal bundle: (x*, y*) = (25, 50).

Exam skill: If you’re allowed to use known results (Cobb–Douglas), do so. But many exams want the Lagrangian steps—practice them.

2.4 From Marshallian Demand to Indirect Utility

Marshallian (uncompensated) demand x(p, m) gives optimal quantity as a function of prices and income.

Indirect utility function:
[
v(p_x, p_y, m) = u(x^(p,m), y^(p,m))
]
Sometimes asked to:

Compare utility across price or income changes
Determine welfare effects qualitatively

Even if the course emphasizes applications, understanding indirect utility helps with welfare analysis later.

2.5 Normal vs Inferior Goods: Income Effects

When income rises:

For normal goods, consumption rises.
For inferior goods, consumption falls.

This matters for:

identifying goods using income elasticity
interpreting welfare outcomes (e.g., subsidies for inferior goods may increase quantity less than proportionally)

2.6 Substitution and Income Effects (Intuition + Structure)

For a price change of good x:

The substitution effect measures change in consumption holding utility constant (or using a compensating variation idea).
The income effect measures change due to real income (purchasing power) shifting.

In typical ECON201 tasks:

Use Slutsky-style reasoning: when price of x rises, substitution generally decreases x, while income effect can reinforce or offset depending on whether x is normal/inferior.

Write this clearly:

If x is normal: both substitution and income effect typically reduce x.
If x is inferior: substitution reduces x, but income effect might increase x (Giffen behavior can occur for certain conditions in models).

2.7 Individual Demand to Market Demand

Market demand is the horizontal sum of individual demands:
[
Q_{market}(p) = \sum_i Q_i(p)
]
If multiple consumers have identical preferences but different incomes, you often:

compute each individual Marshallian demand
sum across individuals

Example: Two consumers with Cobb–Douglas utility u = x^0.5 y^0.5, with p_x = 2, p_y = 1.

Consumer A income m_A = 80 → spend 40 on x → x_A=20
Consumer B income m_B = 120 → spend 60 on x → x_B=30
Total market demand at these prices: x_M=50.

2.8 Demand Functions and Elasticities from Utility Models

Once you have demand functions, you can derive elasticity. For example, if x(p,m) = k·m/p (a proportional rule), then:

x decreases with p
percent changes can be computed directly

Cobb–Douglas often yields straightforward elasticity:

Uncompensated price elasticity for Cobb–Douglas with exponent 0.5 typically equals −1 (for each good), under standard conditions.

2.9 Applications with South African Contexts (Consumer Choice Lens)

Even when the numerical part is abstract, applications can be anchored in real-life categories typically examined in South African curricula:

Transport decisions: choice between minibus taxi/ride-hailing or between private transport and public transport, driven by price and income.
Food consumption: budget shares determine consumption patterns under income changes.
Health-related goods/services: availability of substitutes (private vs public) influences elasticity.
Energy choices: substitution between electricity and alternative sources, especially under price shocks.

For exam writing, your goal is to connect model logic to outcomes:

If a subsidy reduces the effective price of a good, quantity demanded rises—more so when demand is elastic.
If demand is inelastic (e.g., necessities), policy affects welfare but reduces quantity less.

Section 3: Production, Cost Minimization, and Market Structure (Firms in Intermediate Micro)

Consumer theory gives demand; production theory gives supply and cost. ECON201 often connects these to market structures—perfect competition, monopoly, monopolistic competition, and oligopoly—plus pricing and strategic interaction concepts.

3.1 Firms, Technology, and Production Functions

A production function maps inputs to outputs:
[
q = f(L,K)
]
where:

L = labor
K = capital

Common properties:

Positive but diminishing marginal products (at least in standard models)
Diminishing marginal rate of technical substitution (for convex isoquants)

Isoquants represent combinations of L and K producing the same q:

More output corresponds to outer isoquants.

3.2 Cost Minimization: Dual View of Production

A firm that takes prices of inputs (w for labor, r for capital) chooses input combinations to minimize cost for a given output q.

Min problem:
[
\min_{L,K} ; C = wL + rK \quad \text{s.t. } f(L,K)=q
]

Set up a Lagrangian:
[
\mathcal{L} = wL + rK + \mu (q – f(L,K))
]
FOCs yield:

Condition equating MRTS to input price ratio
“Tangency” between isoquant and isocost line

Isocost line:
[
wL + rK = \text{constant}
]

slope = −w/r in (L,K)-space

Tangency principle: at optimum,
[
\text{MRTS}_{LK} = \frac{w}{r}
]

3.3 Short Run vs Long Run

Short run: at least one input fixed (e.g., capital K fixed)
Long run: all inputs variable

This matters for:

shape of cost curves
ability to adjust production scale
elasticity-like comparisons (e.g., long-run supply more elastic)

3.4 Cost Curves: Total, Average, Marginal

Key cost components:

Total cost (TC)
Average cost (AC) = TC/q
Marginal cost (MC) = dTC/dq (or discrete approximation)

Standard relationships:

MC intersects AC at AC’s minimum (under regularity conditions)
MC rising implies AC increases after its minimum

3.5 A Numerical Cost Example (Intersections Matter)

Suppose a firm’s total cost is:
[
TC(q)= 10 + 2q + q^2
]
Then:

MC: derivative of TC:
[
MC(q)= 2 + 2q
]
AC:
[
AC(q)= \frac{10 + 2q + q^2}{q} = \frac{10}{q} + 2 + q
]

Find q where MC = AC:
[
2 + 2q = \frac{10}{q} + 2 + q
]
Cancel 2:
[
2q = \frac{10}{q} + q
\Rightarrow q = \frac{10}{q}
\Rightarrow q^2 = 10
\Rightarrow q = \sqrt{10}
]
At q = √10, AC is minimized.

Exam writing tip: If they ask conceptually, state the intersection property. If they ask numerically, show MC and AC and solve.

3.6 Profit Maximization in Perfect Competition

In perfect competition:

Firm is price taker: market price P is given.
Profit:
[
\pi = pq – TC(q)
]
Maximization:
Choose q where MC = P (for interior solutions)

Condition: produce if P ≥ AVC (average variable cost) in short run; shut down if P < AVC.

This gives:

Firm supply curve corresponds to MC above AVC.

Numerical example:
Use earlier cost: TC(q)=10+2q+q^2.
Assume fixed cost 10, variable cost VC(q)=2q+q^2.

AVC = VC/q = (2q+q^2)/q = 2+q
MC = 2+2q

If market price P = 10:
Set MC = P:
2 + 2q = 10 → 2q = 8 → q = 4.

Check shut-down condition:
P ≥ AVC? AVC at q=4 is 2+4=6; yes 10≥6, so produce.

Profit:

revenue = pq = 10*4=40
TC = 10+2(4)+16=10+8+16=34
π=40−34=6

3.7 Monopoly: Market Power and Marginal Revenue

In monopoly:

Firm faces downward-sloping demand, so marginal revenue MR is below price.
Profit maximization: MC = MR
Output is lower than competitive outcome and price is higher (relative to competition).

If demand is linear:
[
P(Q)=a – bQ
]
Total revenue:
[
TR = P(Q)\cdot Q = aQ – bQ^2
]
Marginal revenue:
[
MR = \frac{dTR}{dQ}= a – 2bQ
]
So MR intercept equals a, but slope is double in magnitude.

Example: demand P = 50 − Q (so a=50, b=1), MC = q + 10 (example).
Set MC=MR:

q + 10 = 50 − 2q
3q = 40
q = 13.333
Price: P = 50 − 13.333 = 36.667

Then compute profit if needed.

3.8 Measuring Welfare: Consumer Surplus and Deadweight Loss

Consumer surplus (CS) in linear demand can be computed:

Area of triangle under demand above price.

Deadweight loss (DWL):

Welfare lost from monopoly relative to efficiency outcome (typically competitive).

In exam questions:

Find competitive Q (where P equals MC in standard efficiency framing)
Find monopoly Q (where MR equals MC)
Compute CS and TS changes, or compute DWL using triangle areas.

3.9 Monopolistic Competition and Product Differentiation

Monopolistic competition features:

many firms
differentiated products
downward demand for each firm

In the long run (with free entry):

economic profits are zero
price equals average cost (P = AC), under the standard model

However, firms maintain some market power because products differ.

Application logic: brand differentiation can make demand more inelastic, affecting pricing and welfare.

3.10 Oligopoly and Strategic Interdependence

In oligopoly:

firms are mutually dependent
pricing decisions affect rivals and vice versa

Key models commonly introduced:

Cournot (quantity competition): choose quantities simultaneously; market price depends on total quantity.
Bertrand (price competition): choose prices simultaneously; price competition can lead to outcomes near competition if products are homogeneous and marginal costs are constant.

In exams, you may be asked:

interpret Nash equilibrium
compute equilibrium output or prices with given demand and cost functions
discuss how collusion affects output and prices

3.11 South African Applications: Firms, Costs, and Market Institutions

South Africa-specific application framing often uses:

market power in utilities or telecoms
transport and retail competition
informal sector constraints and the role of regulations
cost structures affected by energy prices and logistics

In written responses, you typically argue using theory:

If costs rise (e.g., energy input price increases), MC shifts upward → output falls and price rises in monopoly/market power settings.
Under competitive markets, the pass-through depends on elasticities and how much of cost change is marginal vs fixed.

Section 4: Market Failures, Externalities, Public Policy, and Welfare Analysis

Intermediate Microeconomics in applications heavily tests your ability to evaluate whether markets allocate resources efficiently. Market failures include externalities, public goods, information problems, and imperfect competition. This section concentrates on externalities, policy instruments, and welfare calculations, especially the kind of structured answers expected in South African university exams.

4.1 Efficiency and the Role of Marginal Analysis

A central efficiency benchmark:

In competitive efficient outcomes, marginal social cost (MSC) equals marginal social benefit (MSB).

With externalities:

Private costs/benefits differ from social costs/benefits.

If a negative externality exists (e.g., pollution):

MSC > MPC
If a positive externality exists (e.g., vaccination):
MSB > MPB

4.2 Negative Externalities: Diagram Logic and Numerical Form

Suppose:

Private marginal benefit: MB(q) = 100 − q
Private marginal cost: MPC(q) = 20 + 2q
External cost: assume marginal external damage MD(q)= q (so MSC = MPC + MD = 20 + 2q + q = 20 + 3q)

Efficient outcome:
[
MSB = MSC
\Rightarrow 100 – q = 20 + 3q
\Rightarrow 80 = 4q
\Rightarrow q^*_{social} = 20
]

Market outcome (ignoring external damage):
[
MB = MPC
\Rightarrow 100 – q = 20 + 2q
\Rightarrow 80 = 3q
\Rightarrow q^*_{private} = 26.667
]

Thus the market produces too much:

Private/market quantity: 26.667
Socially optimal quantity: 20

Exam writing: Clearly state that with a negative externality, market equilibrium is beyond the efficient quantity because buyers ignore the external cost.

4.3 Policy Instruments: Pigouvian Taxes and Cap-and-Trade

Pigouvian tax

A Pigouvian tax sets per-unit tax equal to marginal external damage at the efficient quantity:
[
t = MD(q_{social})
]
Using MD(q)=q:

at q_social=20 → t = 20

If tax internalizes externality:

MPC increases by t to match MSC.

Cap-and-trade (intuitive justification)

A regulator sets a quantity cap equal to q_social and allows firms to trade permits. The market achieves the environmental target:

firms with lower abatement costs cut more and sell permits
firms with higher abatement costs buy permits

You may be asked: when is cap-and-trade better than tax?

When you care about a specific quantity target
When environmental damage is uncertain but you can monitor emissions effectively
When political or administrative constraints prefer quantity regulation

4.4 Positive Externalities: Subsidies and Public Provision

Positive externality: marginal benefit to society exceeds private benefit.

Example:

MB private: MBp(q) = 40 + 2q? (you can shape as linear)
External benefit adds to MSB.

Efficient output where MSB = MSC will exceed the market output:

market underprovides the good

Policy response:

subsidy to shift private incentives toward socially efficient provision
sometimes public provision if financing and coordination are required (e.g., national campaigns)

4.5 Public Goods and Free Rider Problems (Core Application)

A public good is:

non-excludable (hard to prevent use)
non-rival (one person’s consumption does not reduce others)

Markets often underprovide public goods because individuals can free ride. You may be asked to:

define free rider problem
explain why voluntary contribution fails to reach the socially optimal level
describe policy solutions (tax funding, public provision, or matched subsidies)

In exam answers, a clean structure:

Describe public good properties
Explain why individual incentives diverge from social incentives
Mention government intervention solutions
Use a diagram/logic or a numerical example of underprovision qualitatively

4.6 Externalities in South Africa: Pollution, Health, and Education

South Africa exam contexts frequently include externality interpretations:

Air pollution and transport: congestion and emissions impose external costs.
Public health: vaccination and preventative healthcare generate positive spillovers.
Education: learning spillovers can be framed as positive externalities (workforce productivity beyond individual returns).
Information and consumer protection: information asymmetry can be treated as a related failure (though strictly not an externality, exam questions sometimes connect them).

When asked for policy recommendations:

emphasize efficiency and distribution considerations
note administrative feasibility and monitoring constraints

4.7 Welfare Analysis: Consumer Surplus, Producer Surplus, and Total Surplus

Total surplus:
[
TS = CS + PS
]
Under externalities, total surplus is maximized at the efficient quantity where MSC=MSB.

For taxes/subsidies, government revenue or cost matters:

For a tax with per-unit t and quantity q: government revenue = t·q
Total welfare includes CS + PS + government revenue (minus any external damage costs if modeled)

Important exam skill: Show you can compute the “net” welfare effects of policy—some costs shift to the government, but external damages still matter.

4.8 Counter-arguments and Limitations: When Theory Meets Reality

A strong ECON201 response includes limitations:

taxes require accurate knowledge of marginal external damage
enforcement can be costly
cap-and-trade requires credible monitoring of emissions
information asymmetry can lead to miscalibration

You should also mention behavioral responses:

firms may lobby, evade, or invest differently
consumers may adjust (elasticity changes after policy)

In short, policy design depends on the elasticities and feasibility of measurement.

Section 5: Applications, Government Intervention, and Exam-Style Problem Solving Framework

This final section consolidates skills: how to set up equations, interpret results, and handle common “application” style questions. It also includes structured templates that match how South African exam questions are written: “derive,” “interpret,” “show,” “discuss,” and “evaluate policy.”

5.1 Government Price Controls: Ceilings, Floors, and Welfare Effects

A price ceiling sets P ≤ P_max. If P_max is below equilibrium:

quantity demanded exceeds quantity supplied → shortage
deadweight loss arises
distribution effect may benefit consumers but reduce efficiency

A price floor sets P ≥ P_min. If P_min exceeds equilibrium:

quantity supplied exceeds quantity demanded → surplus
potential waste unless regulated (e.g., procurement)

Exam tasks often ask:

Find shortage/surplus using Qd and Qs at controlled price
Calculate CS/PS changes qualitatively
Evaluate long-run effects: black markets, quality deterioration

Numerical example (price ceiling)

Let:

Qd = 120 − 2P
Qs = 20 + 3P
Competitive equilibrium:
Set equal → 120 − 2P = 20 + 3P → P=20, Q=80.

If government imposes ceiling P=15:

Qd = 120 − 2(15)= 90
Qs = 20 + 3(15)= 65
Shortage = 90 − 65 = 25

Then discuss welfare: consumers benefit from lower price, producers lose surplus, deadweight loss from the quantity gap.

5.2 Subsidies and Tax-Subsidy Interactions

Per-unit subsidy s to consumers effectively reduces consumer price:

If tax increases price faced by the other side, subsidy reverses.

Common policy question:

Compare quantity effects from tax vs subsidy given elasticities
Determine fiscal burden vs revenue

You might be asked to compute:

new equilibrium after subsidy
government cost = s·q

Then interpret distribution:

who benefits (consumers vs producers) depends on elasticities.

5.3 Transfers and Welfare: Distinguishing Efficiency vs Equity

In policy evaluation, two separate criteria matter:

Efficiency (total surplus)
Equity (who gains/loses)

A transfer (like a cash payment) can improve equity without changing efficiency if it doesn’t distort prices. In contrast:

distortionary taxes/subsidies change incentives and can reduce efficiency.

Exam essays may ask: “Is VAT regressive?”
In theory, elasticity and income distribution matter:

if low-income households have more inelastic demand for necessities, taxes may take a larger share of income.
you then argue with income elasticity and budget shares.

5.4 Imperfect Competition Policy: Antitrust and Regulation

In markets with market power (monopoly or collusion), the government may intervene:

antitrust enforcement
regulation of utilities
price caps

You should be able to relate:

monopoly output lower than competitive
higher prices and deadweight loss
regulation can approximate competitive outcomes but requires information about costs

A major exam twist:

regulation may create incentives problems: “regulatory capture” or misreporting costs.

So a good policy evaluation includes:

expected efficiency gains
potential administrative/incentive problems
distributional consequences

5.5 Strategic Interaction Examples (Cournot Setup Template)

Cournot model setup:

Firms choose quantities q1 and q2 simultaneously.
Market price depends on total quantity: Q = q1 + q2.
Each firm maximizes profit given rival quantity.
Find Nash equilibrium.

If demand:
[
P = a – bQ
]
Firm i profit:
[
\pi_i = P(q_1+q_2)q_i – C(q_i)
]
If cost is linear C(q)=cq:
[
\pi_i = (a – b(q_1+q_2))q_i – cq_i
]

FOC:

derivative w.r.t q_i set to zero
solve system of two best-response functions.

In exam conditions, you should show:

best-response derivation
equilibrium q1=q2 if symmetric
compute price and profits

5.6 Nash Equilibrium Reasoning: How to Discuss Without Full Computation

Some exam questions are qualitative: “Explain why dominant strategies lead to equilibrium.”
You can write:

Nash equilibrium = no unilateral profitable deviation
If a strategy is dominant, the equilibrium is that dominant strategy profile
In price competition (Bertrand with identical products), equilibrium can reach marginal cost under certain assumptions.

5.7 A Full Exam-Style Comparative Statics Workflow

A common exam workflow is consistent:

Identify model: competitive, monopoly, externality, price control, tax/subsidy.
Write equations: Qd(P), Qs(P), or demand and cost, or MSC/MPS.
Solve equilibrium: set MB=MC, MR=MC, Qd=Qs, etc.
Compute welfare variables if asked: CS, PS, TS, DWL.
Interpret changes: direction of P and Q (and CS/PS changes).
Link elasticity/strategic reasoning: if incidence or market power asked.

Below is a reusable “template” you can apply in timed exams.

Template: Competitive equilibrium with a tax t

Given:

Qd = A − B·P (consumer price)
Qs = C + D·P (producer price)
Tax implies:
Pc = Pp + t
substitute Pc into demand and Pp into supply

Steps:

Write Qd(Pc) = Qs(Pp) with Pp = Pc − t
Solve for Pc and Pp
Find quantity Q
Compute incidence:
- consumer burden = Pc − P* (pre-tax equilibrium price)
- producer burden = P* − Pp
If asked, compute government revenue = t·Q and welfare loss using DWL approximations if needed.

5.8 Worked Policy Scenario: Externality Tax with Welfare Computation

Return to the externality model in Section 4 but push toward exam-style welfare.

Assume linear curves:

MSB(q) = 100 − q
MSC(q) = 20 + 3q

Efficient quantity:
[
100 – q = 20 + 3q \Rightarrow q_s=20
]
Market quantity:
Private MB equals MPC. Private marginal cost MPC(q) = 20 + 2q.
Market quantity from:
[
100 – q = 20 + 2q \Rightarrow q_p=26.667
]

If exam asks “welfare loss,” compute the triangle between MSB and MSC between q_s and q_p.

DWL area:

horizontal: q_p − q_s = 26.667 − 20 = 6.667
vertical is the gap in marginal benefit vs marginal cost at some point; for linear, use average of end gaps or compute using coordinates.

At q_p: externality leads MSC > MSB.
At q_s: MSC = MSB.

You can compute using end values difference:
Define gap G(q) = MSB − MSC.
G(q) = (100 − q) − (20 + 3q) = 80 − 4q.
At q_s=20: G=80−80=0.
At q_p=26.667: G=80 − 4(26.667)=80−106.668= −26.668.
So magnitude vertical gap is 26.668.

DWL (triangle) = 0.5 * (base)(height) = 0.5(6.667)*(26.668) ≈ 88.89.

Exam caution: Some lecturers prefer symbolic expression or emphasize “qualitative triangle logic.” But if numbers are given, show an approximate calculation and interpret.

5.9 Clustered Institution Focus: Course Delivery and Assessment Patterns

Although “ECON201” is a common course code across many South African institutions, universities typically differ in assessment weighting (tests, assignments, finals) and emphasis (more math vs more application). This study guide focuses on a South African learning approach: build conceptual clarity plus strong quantitative procedure.

Below are five institution-cluster themes that mirror how courses are often delivered. Each cluster focuses on one institution, and each title focuses on specific course offerings at that institution.

Cluster 1 (University of Johannesburg): ECON201 – Intermediate Microeconomics and Applications (Typical Assessment & Skill Priorities)

The University of Johannesburg’s intermediate micro content commonly expects:

early mastery of demand/supply and elasticity computations
careful optimization steps for consumer and firm problems
structured essay responses about market failure and welfare

What to prioritize for UJ-style exams:

Show algebraic steps (not only final answers)
Use clear definitions: e.g., “PED measures responsiveness of quantity demanded to price changes…”
For policy questions, connect elasticity and welfare outcomes

Likely question patterns:

“Compute equilibrium and new equilibrium under tax/subsidy.”
“Compute CS/PS and DWL for a monopoly or externality scenario.”
“Interpret incidence: which side bears the larger share of tax and why.”

Study checklist:

Elasticities: point and arc elasticity
Consumer demand: Lagrangian method for non-Cobb–Douglas preferences
Firm costs: MC/AC/AVC logic
Market structure: MC=MR for monopoly
Externalities: MSC=MSB and Pigouvian tax logic

Cluster 2 (University of Pretoria): ECON201 – Intermediate Microeconomics and Applications (Math-Rigour and Welfare Derivations)

At the University of Pretoria, intermediate micro is often more math-rigorous:

utility maximization and transformations
cost minimization and marginal conditions
welfare and incidence analysis with more derivation

What to prioritize:

Fluency with derivatives and solving systems
Use of marginal analysis rather than only diagram intuition
Ability to compute elasticities from demand functions

Common assessment emphasis:

“Derive the demand function from the utility maximization problem.”
“Obtain MR from a given demand and compute monopoly outcome.”
“Compute welfare effects precisely (areas/triangles with correct formulas).”

How to write a top-grade solution:

Derive demand/supply conditions cleanly.
Solve equilibrium with substituted expressions.
Show the welfare measure formula and compute.

Cluster 3 (University of Cape Town): ECON201 – Intermediate Microeconomics and Applications (Conceptual Explanations + Quant Problems)

At UCT, intermediate micro often tests:

conceptual explanation with formal micro language
ability to blend narrative with mathematics in a single answer

What to prioritize:

Definitions and explanations for substitution vs income effects
Externality policy evaluation (tax vs regulation vs subsidy)
Strategic reasoning in oligopoly (even if computations are moderate)

Common question patterns:

“Discuss why market outcomes are inefficient under externalities and how policy corrects this.”
“Explain substitution vs income effects and derive sign of income effect.”
“Compare tax and cap-and-trade: relative merits and conditions.”

Top-grade approach:

Always include the “why” after computation:
- e.g., “Tax reduces output because it shifts private marginal cost upward toward MSC.”

Cluster 4 (Stellenbosch University): ECON201 – Intermediate Microeconomics and Applications (Production/Cost Focus and Market Power)

Stellenbosch’s intermediate micro often stresses:

production functions and cost relationships
profit maximization logic in different market structures
clear marginal reasoning

What to prioritize:

Cost curve construction and interpretation
Deriving MC, AC, AVC and identifying production conditions
Monopoly pricing outcomes and welfare triangles

Common assessment patterns:

“Given a cost function, compute the profit-maximizing output under monopoly.”
“Determine shut-down output and justify with AVC.”
“Compute DWL under monopoly or under externality with tax.”

Key writing rule:

Always state the relevant condition:
- perfect competition: MC=P
- monopoly: MC=MR
- efficient outcome: MSC=MSB

Cluster 5 (North-West University): ECON201 – Intermediate Microeconomics and Applications (Scenario-Based Applications and Interpreting Results)

North-West University’s applications may lean more toward:

scenario interpretation
connecting micro tools to policy proposals
step-by-step modeling from given text to equations

What to prioritize:

converting real scenarios into micro models
correct interpretation of elasticities and incidence
structured policy evaluation answers

Common question patterns:

“A government sets a price ceiling—predict shortages/surplus and welfare implications.”
“Analyze the effect of a subsidy on quantity and fiscal cost.”
“Evaluate policy to address externalities, including limitations.”

Exam-winning structure:

Translate scenario into model variables.
Solve.
Interpret with economics language.
Discuss limitations or additional considerations.

5.10 Final Consolidation: High-Yield “Must Know” Relations and Signs

To finish effectively, memorize and apply the essential relations. In exams, marks are often allocated for correct setup and sign/inequality reasoning.

Elasticity signs and interpretations

PED for normal downward demand: PED < 0
PES typically positive: PES > 0
Cross-price:
- substitutes: Exy > 0
- complements: Exy < 0
Income elasticity:
- normal goods: EI > 0
- inferior goods: EI < 0

Optimization conditions

Utility max (interior): MRS = price ratio
Cost min: MRTS = w/r
Perfect competition: MC = P
Monopoly: MC = MR
Efficient with externalities: MSC = MSB

Policy direction rules

Negative externality → output too high → tax or regulation to reduce quantity
Positive externality → output too low → subsidy to raise quantity
Price ceiling below equilibrium → shortage
Price floor above equilibrium → surplus

Closing Summary of Core Competencies

ECON201 Intermediate Microeconomics and Applications tests both theory mastery and applied problem solving. If you can confidently:

compute elasticities and incidence,
derive consumer and firm optimality conditions,
analyze monopoly and competitive benchmark outcomes,
evaluate welfare under externalities and policy interventions,

…then you will be prepared for the majority of exam tasks across South African university ECON201 syllabi.

This guide is intentionally built as an integrated set of tools: models connect to each other. Demand depends on preferences and constraints; supply depends on technology and costs; market outcomes depend on incentives and information; and policy impacts depend on both elasticities and welfare implications. Master these links, and exam answers become consistent, accurate, and persuasive.