How do economists approach the world?

(1) Demand and supply (Unit 2), (2) Production possibilities curve (Unit 1), (3) Circular flow of income (Unit 3), (4) AD/AS model (Unit 3), (5) Exchange rate diagrams (Unit 4).

Latin for "all other things being equal." Economists change one variable while holding everything else constant to isolate cause and effect. It is the most important assumption in economic models.

A simplified representation of reality used to understand, explain, and predict economic behaviour. Like a map, it strips away detail to highlight key relationships between variables.

Models use simplifying assumptions (ceteris paribus, rationality) to isolate key relationships, which then generate testable predictions about economic behaviour. The validity of the model is judged by how well its predictions match reality.

The real world is far too complex — millions of variables changing simultaneously. Models simplify reality to isolate key relationships and make testable predictions about cause and effect.

How prices are determined in markets, how equilibrium is reached, and how changes in demand or supply affect price and quantity. It predicts that higher prices reduce quantity demanded and increase quantity supplied, ceteris paribus.

Because usefulness depends on predictive power, not realism. The demand curve assumes perfectly rational consumers — which is unrealistic — but still correctly predicts that quantity demanded falls when price rises. The assumption simplifies without destroying the core insight.

Without it, you cannot determine which variable caused a change. If price, income, AND tastes all change at once, you cannot tell which one affected quantity demanded. Ceteris paribus isolates one cause at a time.

It does not claim the real world actually freezes — it is a mental device that allows economists to isolate one cause-effect relationship at a time. In practice, economists then relax assumptions one by one to approach real-world complexity.

Through graphs, diagrams, equations, and verbal descriptions. For example, the demand and supply diagram is a model, the PPC is a model, and the AD/AS framework is a model.

"If the price of coffee rises, ceteris paribus, the quantity demanded of coffee will fall." This means: assuming income, tastes, prices of other goods, and expectations all stay the same — only price changes.

Because every diagram simplifies reality to show key relationships. A demand curve ignores millions of individual consumers and reduces their behaviour to a single line showing how price affects quantity demanded. That simplification IS the model.

(1) Rational behaviour — consumers maximise utility, firms maximise profit. (2) Ceteris paribus — all other factors held constant. (3) Perfect information — all buyers and sellers have complete knowledge of prices and quality.

By their predictive power — how well they explain and predict real-world outcomes — not by how realistic their assumptions are. A model with unrealistic assumptions can still make useful predictions.

That consumers always make decisions that maximise their utility (satisfaction) given their income and available information. In reality, consumers are often emotional, impulsive, and influenced by biases — which behavioural economics studies.

How income flows between households and firms in an economy. Households provide factors of production and receive income; firms produce goods and receive revenue. The model also shows injections (investment, government spending, exports) and leakages (saving, taxation, imports).

The assumption that all buyers and sellers have complete knowledge of prices, quality, and options available. In reality, information is often incomplete, asymmetric (one side knows more), or costly to obtain — leading to market failures.

Rarely. In reality, many variables change simultaneously. Ceteris paribus is a thinking tool — it helps economists build models and make predictions, but real-world analysis must consider that multiple factors change at once.

Always label axes and key points clearly, show shifts with arrows, identify new equilibrium, and relate the model back to the question. Explain what the model predicts and evaluate whether the prediction holds in reality.

The demand and supply model simplifies a market to just two curves (demand and supply) and shows how price and quantity are determined. It ignores psychology, advertising, seasons, etc. — yet still predicts that higher prices reduce quantity demanded.

A factual claim that can be tested with evidence — it can be proven true or false. It does NOT have to be true; it only has to be testable. Example: "The unemployment rate is 5%."

Economic models are limited by unrealistic assumptions (rationality, ceteris paribus), data imperfections (time lags, measurement errors), the correlation-causation problem, and context-dependency (models that work in one country may fail in another).

Because positive statements are about facts (testable with evidence), while normative statements involve values and priorities. Two economists can agree that a tax will reduce emissions (positive) but disagree on whether the tax SHOULD be imposed (normative).

A value judgement about what should or ought to be. It is based on opinions, beliefs, and values — it cannot be proven true or false with data. Example: "The government should reduce unemployment."

"This model predicts X. However, in reality Y may occur because the assumption of Z may not hold. For example, [real-world example]." This structure shows understanding of the model, awareness of its limits, and application to reality.

Policy debates involve both types. Example: "A carbon tax reduces emissions by 20%" is positive (testable). "The government should impose a carbon tax" is normative (value judgement). Good policy analysis separates what IS from what SHOULD BE.

It captures the core idea: models are simplifications that cannot perfectly represent reality (they are "wrong"), but they are still valuable because they identify patterns, enable predictions, and provide a framework for analysis (they are "useful"). The goal is insight, not perfection.

Distinguish between what IS happening (positive analysis — using data, models, evidence) and what SHOULD happen (normative recommendation — based on values and priorities). This shows sophisticated economic thinking and earns top evaluation marks.

Positive. Even though it is clearly false, it CAN be tested with evidence (scientists have analysed moon samples). A positive statement does not have to be true — it only needs to be testable.

Words like "should", "ought to", "better", "fairer", "too high", "too low", "must", and "needs to." These express value judgements rather than testable facts.

Normative. The word "too" implies a value judgement about what the acceptable level is. "Inflation is 3%" is positive (testable fact), but adding "too" makes it an opinion about whether 3% is acceptable.

It would mean all economists share the same models, values, and data interpretation — which is impossible because economics involves normative judgements about fairness and priorities. Disagreement is healthy and drives better analysis through debate.

Positive statement. It makes a factual claim about cause and effect that can be tested with data. Whether it is actually true is debatable among economists, but it IS testable — economists can study minimum wage changes and measure unemployment effects.

Every topic in Units 2-4 uses models with assumptions. Understanding that models are simplifications with limitations helps you evaluate arguments, discuss real-world applicability, and write balanced essays — skills needed for top marks throughout the course.

Yes. Nearly every economic issue has both. "Raising the minimum wage to $15 increases unemployment by 2%" (positive) vs "We should raise the minimum wage to $15 to reduce poverty" (normative). Economists try to separate facts from judgements.