Opportunity cost = next-best forgone
Opportunity cost is the benefit of the next-best alternative forgone when a choice is made. It exists because resources are scarce: using them for one purpose means they cannot be used for another. Examiners want three elements: it is the alternative given up, it is the next-best one specifically (not all alternatives added up), and it arises from a choice. An example is not required in a 2-mark definition.
Opportunity cost comes from scarcity
The basic economic problem is that resources are scarce (limited) while wants are unlimited. Because of scarcity, every agent must choose how to use resources, and every choice has an opportunity cost — the next-best alternative forgone. So scarcity forces choice, and choice creates opportunity cost. The one exception is a free good (no scarcity, e.g. air), where using it means giving up nothing.
Every decision-maker faces opportunity cost
Opportunity cost shapes every agent's decisions. A consumer spending income on one good gives up the goods it could otherwise buy. A worker taking one job gives up the next-best job's pay, or leisure. A firm using resources for one product gives up the profit on the next-best product. A government funding one programme (say a hospital) gives up the next-best use (say a school). Strong answers name the specific alternative forgone for the agent in the question.
Drawn from real examiner reports.
Define precisely, not by example
On "define opportunity cost", many candidates write only an example ("buying a bag instead of shoes") or a vague phrase like "what you lose". State the concept precisely: the next-best alternative forgone when a choice is made. An example may follow but cannot replace the definition.
November 2022 Paper 22, Q2(a): examiners noted candidates gave examples though a precise definition was what was required.
Explain WHY scarcity always occurs
Asked about the economic problem behind opportunity cost, candidates often state "limited resources and unlimited wants" then stop. Develop the chain: resources are finite, wants are continually renewed and never fully satisfied, so choices must always be made, so opportunity cost always exists. Watch too for candidates who drift onto a different problem such as inflation.
November 2022 Paper 22, Q2(b): candidates stated scarcity/unlimited wants but did not explain why the situation always occurs.
Discuss: develop and support points
On the 8-mark discuss, weak answers "just stated points ... without explaining why they may occur." Do not merely assert "build the hospital" — explain the benefit, explain the opportunity cost (the school forgone), weigh them, and reach a judgement that depends on a condition (e.g. which need is more urgent). Unsupported statements stay at Level 1.
November 2022 Paper 22 key messages and general comments: discuss (d) answers stated points without explanation or development of links.
Opportunity cost vs money cost
Money cost is the price paid. Opportunity cost is the next-best alternative given up, which may differ from the money spent. Waiting two hours in a free queue costs no money but has an opportunity cost — the next-best use of that time. Identify what was actually sacrificed, not just the cash outlay.
It is the next-best, not everything
Opportunity cost is the single next-best alternative forgone — not every alternative added together. If a consumer could have bought a book, a meal or a game, the opportunity cost of the game is only the one thing they would have chosen next (say the book), not the book and the meal combined.
Free good vs economic good
A free good has no scarcity (e.g. air in most situations), so using it means giving up nothing — it has no opportunity cost. Almost every good studied in economics is an economic good: it is scarce, so it does carry an opportunity cost. Do not claim every good has an opportunity cost.
Climb the (a)–(d) command-word ladder
Each rung rewards a different skill: define (2) = the precise concept; explain (4) = one developed point; analyse (6) = connected chains, no judgement; discuss (8) = both sides plus a supported judgement. Answering below the rung caps the mark.
Name the specific alternative forgone
A generic answer says "the government gives up something"; an applied one names it — "the schools it could have built." Always state the specific next-best alternative forgone for the agent in the question. This one move lifts application from Level 1.
Use the four-step pattern for discuss
For a discuss, use the four-step pattern the mark scheme rewards: scarcity -> choice -> the specific alternative forgone -> a judgement that depends on a condition (e.g. which need is more urgent). The conditional judgement is where the AO3 marks sit.
Opportunity cost is the benefit of the next best alternative that is given up (forgone) when a choice is made.
It arises directly from the basic economic problem:
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