IB® · HL/SL
IB® Economics HL/SL
Master every diagram, every evaluation framework, and every command term for IB® Economics.
Start Unit 1 free. 1. Introduction & Microeconomics Foundations is open to everyone, no account needed. Other topics are locked.
1. Introduction & Microeconomics Foundations
THE NATURE OF ECONOMICS
Adam Smith (1723–1790), whose "Wealth of Nations" (1776) founded modern economics. His "invisible hand" describes how self-interested behaviour in competitive markets can, under certain conditions, allocate resources efficiently.
Economics is the social science that studies how individuals, firms, and governments allocate scarce resources to satisfy unlimited wants. The fundamental problem is scarcity: resources are finite, wants are unlimited: choice is unavoidable. Every economy must answer three central questions:
- What to produce (which goods and services).
- How to produce them (which combinations of resources and technology).
- For whom to produce (how output is distributed).
Economics is split into microeconomics (individual markets, firms, and households: Unit 2, plus theory of the firm at HL) and macroeconomics (whole-economy measures: growth, inflation, unemployment, the global economy: Units 3 & 4).
SCARCITY, CHOICE & OPPORTUNITY COST
Because resources are scarce, every choice involves a trade-off: choosing one option means giving up the next best alternative. Opportunity cost = the value of the next best alternative forgone.
- Individual: spending an evening studying has the opportunity cost of the leisure forgone.
- Firm: investing in new machinery has the opportunity cost of the next best use of those funds, such as hiring extra staff or the interest the money could have earned.
- Government: $1 billion on hospitals has the opportunity cost of $1 billion of schools not built.
Free goods (e.g., air, sunlight) have no opportunity cost. Economic goods are scarce and have an opportunity cost.
PRACTICE: NAME THE OPPORTUNITY COST
| Choice | Next best alternative forgone | Opportunity cost |
|---|---|---|
| A student takes a paid weekend job | Studying for the IB exams | The study time (and perhaps a higher grade) |
| A farmer plants wheat on a field | Planting maize on the same field | The maize that could have been grown |
| A government spends $2 billion on a new airport | Building hospitals with the same funds | The hospitals not built |
| A firm keeps $1 million as cash | Investing it at 5% a year | About $50,000 of interest a year |
| People breathe air | Nothing: air is a free good | Zero |
Opportunity cost is the single next best alternative, not the sum of every alternative, and it need not be measured in money: time, output and well-being all count.
FACTORS OF PRODUCTION
Resources used to produce goods and services. Each earns a corresponding factor income.
- Land: natural resources (minerals, forests, water). Earns rent.
- Labour: human effort, mental and physical. Earns wages.
- Capital: man-made goods used to produce other goods (machinery, factories, infrastructure). Earns interest.
- Entrepreneurship: organising the other factors and bearing risk to produce output. Earns profit.
Note on "capital": as a factor of production, capital means produced means of production: physical assets used to make other goods (machinery, tools, factories, infrastructure). It does not include money or financial assets in this technical sense: money simply helps purchase physical capital. The "financial capital" you hear about in everyday speech is a separate concept.
THE NINE CENTRAL IB CONCEPTS
The IB Economics syllabus is organised around 9 key concepts that recur across every unit:
- Scarcity: finite resources vs unlimited wants.
- Choice: selecting among alternatives.
- Efficiency: getting maximum output from inputs (productive efficiency); allocating resources to where they create the most value (allocative efficiency).
- Equity: fairness in the distribution of income, wealth, opportunities.
- Economic well-being: material and non-material aspects of welfare.
- Sustainability: meeting current needs without compromising future generations.
- Change: economies evolve through technology, demographics, policy.
- Interdependence: economic agents and economies are linked through markets and trade.
- Intervention: government action to correct market failures or pursue social goals.
ECONOMIC METHODOLOGY
Models are simplified representations of reality used to analyse cause and effect. All economic models rely on assumptions: most commonly ceteris paribus ("all other things equal") to isolate one variable's effect at a time. Positive economics: factual, testable statements about what is. e.g., "The unemployment rate rose to last quarter." Normative economics: value-laden statements about what should be. e.g., "The government should reduce unemployment." Often signalled by "should", "ought", "better", or "fair". Both types matter: positive economics describes the world; normative economics drives policy debate.
PRACTICE: POSITIVE OR NORMATIVE?
| Statement | Type | Why |
|---|---|---|
| "Youth unemployment rose to 14% last year." | Positive | Can be checked against data |
| "A sugar tax would reduce sugar consumption." | Positive | A testable prediction, even if it turns out wrong |
| "The government should raise the minimum wage." | Normative | Contains a value judgement ("should") |
| "Income inequality in this country is unfair." | Normative | "Unfair" depends on values about equity |
| "If interest rates rise, borrowing tends to fall." | Positive | A cause-and-effect claim that evidence can test or refute |
A positive statement can be false and still be positive: what matters is whether evidence could settle it.
THE PRODUCTION POSSIBILITY CURVE (PPC)
A model showing the maximum combinations of two goods an economy can produce with its given resources and technology.
Key features
- Inside the curve: productive inefficiency (resources unemployed or misallocated).
- On the curve: productive efficiency (maximum output for given resources).
- Outside the curve: currently unattainable (would require more or better resources).
- Slope: opportunity cost of one good in terms of the other. A bowed-out (concave) PPC shows increasing opportunity costs (resources are not perfectly transferable between uses); a straight-line PPC shows constant opportunity costs.
Constant versus increasing opportunity cost A straight-line PPC means resources are equally suited to both goods. A bowed-out PPC shows opportunity cost rising as more of one good is produced.
WORKED EXAMPLE: OPPORTUNITY COST FROM A PPC TABLE
An economy can produce these combinations of food and machines when its resources are fully employed:
| Point | Food (tonnes) | Machines |
|---|---|---|
| A | 0 | 100 |
| B | 20 | 98 |
| C | 40 | 92 |
| D | 60 | 80 |
| E | 80 | 60 |
| F | 100 | 0 |
- Step 1: find what is given up at each step. A to B costs 2 machines; B to C, 6; C to D, 12; D to E, 20; E to F, 60.
- Step 2: divide by the 20 extra tonnes gained each time. The opportunity cost of one tonne of food rises from 0.1 to 0.3, 0.6, 1 and finally 3 machines.
- Step 3: interpret. The rising cost means resources are not equally suited to both goods: the last land and workers moved into farming are the ones best at making machines. That is why this PPC is bowed out (concave).
A combination of 40 tonnes of food and 80 machines lies inside the curve (idle or misallocated resources), while 60 tonnes and 92 machines lies outside it (unattainable for now).
ECONOMIC GROWTH ON THE PPC
Actual growth = movement from inside the PPC toward the curve (using existing resources more fully). Potential growth = an outward shift of the entire PPC, caused by:
- Increase in quantity of factors of production (more labour, more capital).
- Improvement in quality of factors (better education, healthier workforce, R&D).
- Improvements in technology (allowing more output per input).
A biased outward shift (PPC pivots) shows growth concentrated in one sector. Trade-off: producing more capital goods today (instead of consumer goods) shifts the PPC further out tomorrow: current consumption sacrificed for future growth.
Choice, unemployment and growth on the PPC Moving along the curve shows choice and opportunity cost. Moving from inside to the curve is actual growth; an outward shift is growth in production possibilities.
PRACTICE: MOVEMENT, INSIDE POINT OR SHIFT?
| Event | Effect in the PPC model |
|---|---|
| A recession leaves 8% of workers unemployed | The economy moves to a point inside the PPC |
| Unemployed workers find jobs again | Movement from inside toward the PPC (actual growth) |
| Society chooses more capital goods and fewer consumer goods | Movement along the PPC |
| Net migration adds 500,000 workers | The PPC shifts outward (more factors of production) |
| A new vaccine cuts working days lost to illness | The PPC shifts outward (better quality of labour) |
| A drought destroys farmland | The PPC shifts inward |
| A breakthrough in battery technology | A biased outward shift: output of goods that use batteries can rise most |
WORKED EXAMPLE: A PAPER 1 (a)-STYLE ANSWER PLAN
Question: Using a PPC diagram, explain the difference between actual economic growth and growth in production possibilities. (Paper 1 part (a) questions are worth up to 10 marks.)
- Define both terms precisely: actual growth is an increase in real output from using existing resources more fully; growth in production possibilities is an increase in the economy's maximum potential output.
- Draw one correctly labelled diagram (both axes named for the two goods, PPC₁ and PPC₂, and a point inside PPC₁), like the right panel of the figure above.
- Explain each movement: the arrow from the inside point to PPC₁ shows unemployed resources being brought back into use; the outward shift to PPC₂ needs more or better factors of production, or better technology.
- Apply briefly: for example, recovery from a recession (actual growth) versus investment in education or infrastructure (growth in production possibilities).
Part (a) does not ask you to evaluate, so spend the time on accurate definitions, a clear diagram and an explanation that refers to the diagram.
ECONOMIC SYSTEMS
Different ways of answering the three central questions.
- Free-market: resource allocation mainly by price signals through markets; private ownership of factors; limited government intervention. Often associated with capitalism, although real capitalist economies typically involve substantial state activity (so "free-market" describes a theoretical extreme rather than any actual modern economy). Strengths: incentives, efficiency, choice. Weaknesses: inequality, market failures.
- Command (planned): central planners allocate resources; state ownership of factors. Strengths: clear social goals, equity. Weaknesses: information problems, inefficiency, no consumer sovereignty.
- Mixed economy: combination: markets allocate most resources; government corrects market failures and provides public goods. Almost all real economies are mixed, varying in the balance.
The circular flow of income model (1.1)
The circular flow shows how decision-makers in an economy are interdependent. Households own the factors of production and sell their services to firms in return for factor incomes (rent, wages, interest and profit). Households then spend their income on the goods and services that firms produce. In this simple loop, national output, national income and national expenditure are equal.
- Leakages (withdrawals) take money out of the flow: saving (S), taxes (T) and spending on imports (M).
- Injections add money to the flow: investment (I), government spending (G) and exports (X).
- If injections exceed leakages, national income rises; if leakages exceed injections, it falls.
The circular flow of income Income flows from firms to households and spending flows back. Saving, taxes and imports leak out; investment, government spending and exports are injected.
WORKED EXAMPLE: LEAKAGES VERSUS INJECTIONS
In one year an economy has saving of $120 billion, taxes of $200 billion and imports of $180 billion. Firms invest $150 billion, the government spends $220 billion and exports are $160 billion.
- Leakages: S + T + M = 120 + 200 + 180 = $500 billion.
- Injections: I + G + X = 150 + 220 + 160 = $530 billion.
- Conclusion: injections exceed leakages by $30 billion, so spending in the circular flow rises and national income increases until leakages grow to match injections.
Each pair need not balance on its own: here G is above T (a budget deficit) while X is below M (a trade deficit).
RATIONAL CHOICE & ITS LIMITS
Standard economic theory assumes agents are rational: pursuing their own self-interest with full information and consistent preferences.
Behavioural economics (covered more deeply in Unit 2) challenges this
- Bounded rationality: information and computational limits force people to use rules of thumb.
- Cognitive biases: anchoring, framing, loss aversion, overconfidence systematically distort choices.
- Bounded self-interest: people care about fairness and reciprocity, not just narrow gain.
This matters because policies designed assuming perfect rationality often work imperfectly in practice.
SUSTAINABILITY & THE NEW SYLLABUS
Sustainable development = development that meets the needs of the present without compromising the ability of future generations to meet their own needs (Brundtland definition, ). Sustainability connects to environmental, social, and economic dimensions and is a recurring lens applied throughout the syllabus: most notably in:
- Common access resources & negative externalities (Unit 2 micro).
- Sustainable economic growth and supply-side policy (Unit 3 macro).
- Sustainable development goals and barriers to development (Unit 4 global).
SIX REAL-WORLD ISSUES EXPLORED THROUGH NINE KEY CONCEPTS
The official IB Economics course is built around six real-world issues, examined using the nine key concepts above. The six issues, paraphrased: 1. How do consumers and producers make choices in pursuing their economic objectives? (Unit 2 micro) 2. When are markets unable to meet important economic objectives, and is government intervention helpful? (Unit 2 micro) 3. Why does economic activity vary over time, and why does it matter? (Unit 3 macro) 4. How do governments manage the economy, and how effective are their policies? (Unit 3 macro) 5. Who are the winners and losers from the integration of the world's economies? (Unit 4 global) 6. Why is economic development uneven? (Unit 4 global) These six questions are revisited throughout the course, with each unit linking explicitly to the nine key concepts (scarcity, choice, efficiency, equity, well-being, sustainability, change, interdependence, intervention). (See the dedicated "Assessment & Internal Assessment" topic for the full IA requirements.)
COMMAND TERMS: WHAT EXAMINERS ASK
IB exam questions are built from command terms with specific meanings:
- Define / State: give the meaning (1–2 marks).
- Describe / Outline: paint a picture (low-mid marks).
- Explain: give reasons or causes (mid marks).
- Distinguish: set out the differences between two ideas.
- Examine: consider the underlying assumptions and interrelationships.
- Discuss / Evaluate / To what extent, present a balanced argument with judgement (high marks; require evaluation, multiple perspectives, short-run vs long-run, who gains/loses, assumptions).
Key Terms
Scarcity
The fundamental economic problem: resources are finite but human wants are unlimited, forcing choice.
Opportunity Cost
The value of the next best alternative forgone when a choice is made. Distinct from accounting cost: covers all alternatives, not just monetary outlay.
Factors of Production
Resources used to make goods and services: land (natural), labour (human), capital (man-made productive assets), and entrepreneurship (organisation and risk-bearing).
Production Possibility Curve (PPC)
A model showing the maximum combinations of two goods an economy can produce with given resources and technology. Inside = inefficient; on = efficient; outside = unattainable.
Increasing Opportunity Cost
A bowed-out (concave) PPC indicates that as more of one good is produced, increasing amounts of the other must be given up: because resources are not perfectly transferable between uses.
Ceteris Paribus
Latin for "all other things equal". A foundational assumption in economic models that holds other variables constant to isolate the effect of one.
Positive Economics
Statements that describe what is: testable against evidence (e.g., "Inflation rose by ").
Normative Economics
Statements that prescribe what should be: value judgements (e.g., "Inequality is too high").
Free-market Economy
Resource allocation by the price mechanism; private ownership; minimal government intervention. In practice, only a theoretical extreme.
Command Economy
Resource allocation decided centrally by the state; public ownership; central plans replace market signals.
Mixed Economy
A blend of markets and government intervention. Almost all real-world economies are mixed; they differ in degree.
Sustainable Development
"Development that meets the needs of the present without compromising the ability of future generations to meet their own needs" (Brundtland, ).
Bounded Rationality
A behavioural-economics insight: real decision-makers face cognitive and informational limits, so they use heuristics rather than fully optimising: undermining the strict rational-choice assumption.
Exam Tips
- Define everything: IB rewards crisp definitions. Clear, accurate definitions of key terms, "scarcity", "opportunity cost", "PPC", typically help secure the early AO1 (knowledge and understanding) marks in extended responses, even when the question does not explicitly ask. Markschemes don't allocate definition marks mechanically, but they reward the precision that strong definitions enable.
- PPC diagrams: label axes (e.g., "Capital goods" / "Consumer goods"), mark points inside (inefficient) / on (efficient) / outside (unattainable). For "increasing opportunity costs", draw a bowed-out curve.
- Opportunity cost in essays: always express it as "what is given up", not "what is gained". A favourite IB pitfall: students confuse opportunity cost with the price paid: they're different.
- Positive vs normative: scan for "should", "ought", "better", "fair", "unacceptable" → normative. Without them, the statement is positive (factual / testable).
- Real-world examples: top-mark IA commentaries are built on real-world news articles, and Paper 1 / Paper 3 answers benefit from concrete contextual examples. Paper 2 is data-response, so prioritise close use of the stimulus and connect to outside real-world context only where appropriate. Keep notes on – headline stories per real-world issue.
- Command terms decide the answer: a "discuss" answer must include balanced evaluation (pros, cons, who gains, short vs long-run, assumptions). A "state" answer should be one sentence. Match scope to the verb, and check the command term before you start: a "discuss" answer that only describes the topic loses marks however good the description.
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