Thinking like an economist

Economics is a social science: it studies how people and institutions behave, using the scientific method — observe, hypothesise, model, test against evidence.

• Models are deliberate simplifications of reality. They must make assumptions (e.g. that consumers are rational) to isolate one relationship at a time.
• Ceteris paribus — Latin for "all other things being equal". When we say "a fall in price raises quantity demanded", we hold income, tastes and other prices constant. Without ceteris paribus you could never separate one cause from another.
• Economists cannot run controlled laboratory experiments on a whole economy. You cannot re-run 2008 with a different interest rate. So economists rely on natural experiments, historical data and econometrics — which is why economists disagree.

Evaluation hook: a model is only as good as its assumptions. If consumers are not rational (see 1.2.10), a model built on utility maximisation may predict badly. Always ask: which assumption is doing the work here?

Positive vs normative statements

• A positive statement is objective and can in principle be tested against evidence and found true or false. "A 10% rise in the price of cigarettes reduces quantity demanded by 4%."
• A normative statement contains a value judgement — an opinion about what ought to be. "The government should raise cigarette taxes."

Why it matters: value judgements drive policy. Two economists can agree completely on the positive economics (a carbon tax will cut emissions by X and cost the poorest households Y) and still disagree on the normative question of whether it should be introduced, because they weight equity and efficiency differently.

Trap: a statement can be positive and wrong. "Raising the minimum wage always destroys 500,000 jobs" is positive (testable) — and false. Positive does not mean correct; it means falsifiable.

Positive or normative?

Scarcity: the fundamental economic problem

Resources — the factors of production — are finite:

• Land — all natural resources. Split into renewable (fish stocks, forests, solar — replenish naturally if not over-exploited) and non-renewable (oil, coal, iron ore — a finite stock, using it today means it is gone forever).
• Labour — human effort. Capital — man-made aids to production. Enterprise — risk-taking that combines the other three.

Because resources are scarce, every economy must answer three questions: What to produce? How to produce it? For whom?

Opportunity cost

It applies to all three economic agents:

• Consumers: spending £1,200 on a phone means forgoing the holiday you would otherwise have taken.
• Producers: using a factory line for SUVs means forgoing the profit from making saloons on it.
• Government: £2.5bn on a hospital is £2.5bn not spent on schools, defence or tax cuts.

Free goods vs economic goods: a free good (sunlight, air in an unpolluted world) has zero opportunity cost — consuming it does not deny anyone else. An economic good is scarce and therefore has an opportunity cost. Almost everything you study in economics is an economic good.

Your turn — opportunity cost of a budget

The production possibility frontier

A PPF shows the maximum combinations of two goods an economy can produce when all resources are used fully and efficiently, with current technology.

• The PPF is drawn concave to the origin (bowed out) because resources are not equally suited to both uses. As you switch more resources into consumer goods, you must give up increasing amounts of capital goods — increasing opportunity cost.
• The gradient of the PPF at any point is the marginal opportunity cost of one good in terms of the other.

Movements along vs shifts of the PPF

• A movement along the PPF is a reallocation of existing resources — you gain one good only by sacrificing the other. This shows opportunity cost.
• A shift outwards is economic growth in productive potential: more/better resources. Causes: net investment, immigration of workers, education and training, technological advance, discovery of new resources.
• A shift inwards is economic decline: war, natural disaster, mass emigration, depletion of a non-renewable resource.

Capital vs consumer goods — the key trade-off: capital goods are used to produce other goods (machines, factories, infrastructure). Consumer goods give immediate utility (food, clothes, phones).

The dynamic point examiners love: an economy that chooses a point with more capital goods today sacrifices current consumption, but the extra capital shifts the PPF further out tomorrow. So today's opportunity cost buys tomorrow's growth. This is the intertemporal trade-off — and it is exactly why investment matters (Theme 2.2.3).

Your turn — marginal opportunity cost on a PPF

Reading the PPF

Adam Smith and the division of labour

In The Wealth of Nations (1776), Adam Smith described a pin factory. One untrained worker doing every task might make 20 pins a day. Ten workers, each specialising in one of eighteen distinct operations, produced 48,000 pins a day — 4,800 each. That is 240× the output per worker.

Advantages: workers become more skilled at one task; less time wasted switching tasks; easier to mechanise a narrow task; higher output per worker cuts average costs, so firms can charge lower prices and compete internationally.

Disadvantages: work becomes repetitive and boring — lower morale, higher absenteeism and turnover; workers become structurally unemployable if their one skill dies out (Theme 2.1.3); production becomes interdependent, so one broken link halts the whole chain; products may become standardised and less varied.

Specialising to trade: countries specialise too. Gains: greater world output, economies of scale, lower prices, more choice. Risks: over-dependence on one export (an oil-dependent economy is exposed to a price crash), depletion of finite resources, and vulnerability to supply-chain shocks.

Why specialisation needs money

Specialisation is impossible under barter, which requires a double coincidence of wants. Money solves this. It has four functions:

• Medium of exchange — universally accepted in payment, so no double coincidence of wants is needed.
• Measure of value (unit of account) — puts all goods on one scale so relative prices can be compared.
• Store of value — holds purchasing power over time, so you can sell today and buy later. Inflation erodes this function (link to Theme 2.1.2).
• Method of deferred payment — allows credit and contracts denominated in money.

Match the thinker or term to the idea

Tap an idea on the left, then its matching thinker or term on the right.

Free market, command and mixed economies

Every system answers what / how / for whom — they differ in who decides.

• Free market — resources allocated by the price mechanism. Adam Smith's "invisible hand": self-interested individuals, guided by prices, unintentionally serve the social interest. Friedrich Hayek went further in The Road to Serfdom: the knowledge needed to run an economy is dispersed among millions of people, so no central planner could ever gather it — prices are how that knowledge gets transmitted.
• Command — the state owns the means of production and planners set output and prices. Karl Marx argued capitalism exploits labour and that the means of production should be commonly owned.
• Mixed — both. In practice every real economy is mixed; the question is only the size of the state.

Evaluation: free markets deliver efficiency, choice and dynamic innovation (profit incentive) but produce inequality, ignore externalities and under-provide public goods (Theme 1.3). Command economies can achieve equity and full employment but suffer information failure, weak incentives, shortages and surpluses. The role of the state in a mixed economy is to do what markets cannot: provide public goods, correct externalities, regulate monopoly and redistribute income.

Sort the features by economic system

Tap a card, then tap the system it belongs to.

Evaluating the division of labour

How to evaluate in Theme 1.1

• Challenge the assumption. The PPF assumes only two goods, fixed technology and full efficiency. Real economies have millions of goods and are almost never on the frontier — the model still earns its keep as a way of showing scarcity, choice and cost.
• It depends on the time period. Building capital goods lowers consumption now but raises the PPF later. Whether that is worth it depends on how much society discounts the future.
• It depends on the magnitude. A small outward PPF shift means nothing if resources stay unemployed inside the curve.
• Whose value judgement? "The state should be smaller" is normative. Push the argument back to the positive question: does the market fail here, and would the state fail worse (Theme 1.4.2)?

Top-band habit: never leave an evaluation as "however, it depends". Say what it depends on, which direction that pushes the answer, and why that matters more or less than your main argument.

Hayek vs the planner

The big ideas to know

Press Finish to see your score.