Opportunity Cost
Contents: 13 sections
What is opportunity cost?
Opportunity cost is the next best alternative given up when a choice is made.
Two parts of that definition earn the marks, and both must be there:
- Next best: not everything you gave up, just the single best option you rejected. If you had $10 and could buy a book, a film ticket or a meal, and you buy the book, the opportunity cost is whichever one of the other two you would have picked.
- Given up: it is a real cost even though no extra money changes hands.
- Scarcity
- choice
- opportunity cost. Every choice has one, because resources are limited.
Opportunity cost is not the same as money cost
This distinction is where most marks are lost.
The money cost is the price paid. The opportunity cost is what that money (or time) could have done instead.
They can be very different:
- A student who stays in education pays fees, but the opportunity cost also includes the wages they could have earned by working instead. That is often the bigger cost.
- A farmer who uses their own field pays no rent, so the money cost looks like zero, but the opportunity cost is the rent they could have received by letting someone else use it.
Occasionally opportunity cost is zero: if a resource has no other use at all, giving it up costs nothing. A completely idle machine put back to work has no opportunity cost.
Who faces opportunity cost?
The exam almost always attaches this to a specific group, so practise applying it:
| Group | Choice | Opportunity cost |
|---|---|---|
| Consumers | Limited income | The next best good they did not buy |
| Workers | Limited time | The next best job, or leisure time given up |
| Firms | Limited finance | The next best investment not made |
| Governments | Limited tax revenue | The next best public service not funded |
Governments are the most commonly examined. Every budget decision is an opportunity cost decision: money spent on defence cannot be spent on healthcare.
How opportunity cost influences decisions
Decision-makers compare the benefit of a choice against what they give up:
- A consumer buys the good giving the most satisfaction per dollar.
- A firm chooses the project with the highest expected profit, giving up the next best.
- A government weighs the benefits of each service against the alternatives.
This is why opportunity cost is not just a definition; it is the reason resources end up allocated one way rather than another.
Worked example
A student is deciding between two options after school:
- Take a job paying $18,000 a year
- Study full time, with fees of $4,000 a year
Money cost of studying = $4,000 (the fees).
Opportunity cost of studying = the $18,000 of wages given up, plus the $4,000 that could have been spent on something else, the next best use of both the time and the money.
The true cost of studying is therefore much higher than the fee alone. That is exactly why opportunity cost matters: looking only at money cost leads to a bad decision.
The other side. If studying raises future earnings by more than that; it is still worth doing, the decision compares the benefit against the opportunity cost, not against zero.
Common exam mistakes
- Defining opportunity cost as "what you gave up" without saying next best.
- Listing every alternative rather than the single best one.
- Giving the answer in money when the question wants the forgone item.
- Confusing money cost with opportunity cost.
- Saying a choice has no opportunity cost simply because it was free of charge.
Exam technique
Learn the definition word for word: "the next best alternative given up when a choice is made." These are usually 2-mark questions and the marks go to precision.
When the question names a group or a situation, give the opportunity cost from that context. "The opportunity cost is the new school the government did not build" earns more than a general definition.
For longer answers, show you understand it is about real resources, not just money, the student example above is the clearest way to do that.
Building an answer
2 marks, "Define opportunity cost."
Opportunity cost is the benefit of the next best alternative given up when a choice is made.
Next best is the mark. "What you give up" is too loose, you give up every other option, but the opportunity cost is only the single best one you forgo.
4 marks, "Explain the opportunity cost to a student of staying in education."
The direct cost is the fees and materials paid for.
The opportunity cost, however, is the wage that could have been earned by taking a job for those years instead, the next best use of that time.
There may also be a non-financial element: the leisure or work experience given up.
Examiners look for the forgone earnings. An answer that lists only fees has described the financial cost and missed the concept entirely.
6 marks, "Analyse the opportunity cost to a government of building a new airport."
The financial outlay is the construction budget, but the opportunity cost is what that budget would otherwise have funded, perhaps a hospital, or a reduction in taxation.
Land is also given up: the site could have been farmland or housing, so its next best use is forgone.
The workers and materials employed on the airport are unavailable for other projects, so the cost is real resources, not merely money.
Because the government operates on the production possibility curve, choosing more of one thing necessarily means less of another.
Where the marks are lost
The three errors examiners report most, in order:
- Listing everything given up rather than the single next best alternative.
- Confusing opportunity cost with financial cost. A free-to-use service still has an opportunity cost, because the resources could have been used elsewhere.
- Claiming a free good has an opportunity cost. If a good is not scarce, nothing is forgone by using it; that is the definition of a free good.
A real case to quote
The 2012 London Olympics. The stated cost was about £9 billion. The opportunity cost was what that £9 billion, that land in Stratford, and the construction workforce would otherwise have produced, schools, transport, housing. Whether the Games were worth it is a normative question; the opportunity cost is the positive one, and it is measured in the alternatives forgone.
Definitions the mark scheme accepts
| Term | Definition to learn |
|---|---|
| Opportunity cost | The benefit of the next best alternative forgone |
| Trade-off | Giving up some of one thing to gain more of another |
| Free good | Has no opportunity cost because it is not scarce |
| Production possibility curve | Shows the maximum combinations of two goods an economy can produce using all resources efficiently |
Quick revision
- Opportunity cost = the next best alternative given up.
- It exists because resources are scarce and choices must be made.
- Money cost ≠ opportunity cost. Studying costs fees and forgone wages.
- Applies to consumers, workers, firms and governments.
- Can be zero if the resource has no other use.
- Always state the cost as the thing given up, not as an amount of money.
Check you have it
Question 1
In recent years more golf courses, which use large quantities of water, have opened in China. What may be the opportunity cost of this?
Answer: B.
Opportunity cost is the best alternative given up. Land and water devoted to golf courses cannot also be used for agriculture, and the question emphasises that golf courses consume large quantities of water, a scarce resource in much of China. What is sacrificed is therefore the farming output that the land and water would otherwise have produced. That forgone farmland is the opportunity cost.
Why the other options are wrong:
- A, the cost of water, is a money cost of running the golf course. It tells you what the operator pays, not what alternative use was given up. The two are related but distinct ideas.
- C, sales of golf equipment, is a benefit arising from the courses opening, and a benefit to a different industry at that. Opportunity cost is always the loss, never the gain.
- D, wages of golf course staff, is another money cost of operating the business, and it also represents employment created rather than sacrificed.
Question 2
A government reduces social security spending by $10 bn in order to increase defence spending
by $10 bn.
What is this an example of?
Answer: D.
The government has cut $10bn from one area and added exactly $10bn to another, so total spending is unchanged. What has changed is where the resources go: labour, capital and materials are moved out of social security provision and into defence. Shifting resources between competing uses without changing the total is the definition of a reallocation, and it illustrates opportunity cost in action, the extra defence output is obtained by giving up social security provision.
Why the other options are wrong:
- A, expansionary fiscal policy, would require an increase in total government spending or a cut in taxation, so that aggregate demand rises. Here the two changes cancel exactly, so the fiscal stance is unchanged.
- B, market forces, means allocation by supply and demand through the price mechanism. This is a government decision, so resources are being directed administratively rather than by prices.
- C, price stability, refers to keeping inflation low and steady. Nothing here concerns the general price level.
Question 3
A student decides to buy a ticket for a concert instead of buying a new shirt. What is the opportunity cost of buying the ticket?
Answer: C.
Opportunity cost is the best alternative given up when a choice is made. The student had the money for one purchase and chose the concert ticket, so what was sacrificed is the shirt. Opportunity cost is always measured in terms of the thing forgone, not the thing obtained and not the money spent.
Why the other options are wrong:
- A, the concert, is what the student gained. Opportunity cost is the loss, not the benefit.
- B, the price of the ticket, is the money cost. This is the commonest confusion in the topic: the price tells you how much was spent, while the opportunity cost tells you what that money could have bought instead. The two are different ideas even though they are linked.
- D, the time spent purchasing the ticket, is a genuine cost of the transaction, and the alternative uses of that time do carry an opportunity cost of their own. But the question asks about the choice between the ticket and the shirt, and the shirt is the alternative that was actually given up.
What the syllabus asks for on this topicSyllabus points
Syllabus points
- Define opportunity cost and its influence on decision-making.
- Explain how opportunity cost applies to consumers, workers, firms and governments.
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