Current syllabus: 2026–2028, Version 2 Official syllabus points: 6.1.1–6.1.4

Current Cambridge requirements

This topic must cover:

the distinction between absolute advantage and comparative advantage;
the benefits of specialisation and free trade (trade liberalisation), including the trading possibility curve;
exports, imports and the terms of trade, including measurement, causes of changes and impacts of changes;
limitations of the theories of absolute and comparative advantage.

The current Cambridge syllabus is the controlling source. Older Excel in Economics notes are used as a secondary teaching and artwork library. Their useful opportunity-cost tables, PPC examples and terms-of-trade discussions have been retained where accurate, but old syllabus ordering, copied examination screenshots and several incorrect shortcuts have been rejected.

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Exam Essentials

1. Why countries trade

Countries trade because they differ in:

natural-resource endowments;
climate and geography;
labour quantity, skills and wage costs;
capital, technology and infrastructure;
productivity and production costs;
consumer preferences;
the scale of their domestic markets.

These differences create opportunities for countries to specialise in goods and services they can produce at a lower opportunity cost and exchange them for other products.

An export is a good or service sold by residents of one country to non-residents. An import is a good or service bought by residents of one country from non-residents.

Free trade means international exchange with few or no artificial barriers such as tariffs, quotas or embargoes. Trade liberalisation is the process of reducing or removing such barriers.

Free trade does not mean trade has no real costs. Transport, insurance, information, finance and compliance costs can remain even when policy barriers are absent.

2. Absolute advantage

A country has an absolute advantage in a product when it can:

produce more of that product using the same quantity of resources; or
produce the same quantity using fewer resources.

Suppose one unit of resources can produce the following maximum outputs:

Country	Wheat	Cars
Aralia	80	20
Borland	60	15

Aralia has an absolute advantage in both products because it can produce more wheat and more cars with the same resources.

Absolute advantage compares productivity or resource requirements. It does not by itself identify the best pattern of specialisation.

3. Comparative advantage

A country has a comparative advantage in a product when it can produce it at a lower opportunity cost than another country.

Comparative advantage is therefore about what must be sacrificed, not simply which country can produce the largest quantity.

Using the table above:

Aralia

Opportunity cost of 1 car = 80 wheat ÷ 20 cars = 4 wheat.
Opportunity cost of 1 wheat = 20 cars ÷ 80 wheat = 0.25 cars.

Borland

Opportunity cost of 1 car = 60 wheat ÷ 15 cars = 4 wheat.
Opportunity cost of 1 wheat = 15 cars ÷ 60 wheat = 0.25 cars.

Here the opportunity costs are identical. Neither country has a comparative advantage, so the simple model does not generate gains from specialisation between them.

Now change Borland’s car maximum to 10:

Country	Wheat	Cars
Aralia	80	20
Borland	60	10

Aralia’s opportunity cost of 1 car = 4 wheat.
Borland’s opportunity cost of 1 car = 6 wheat.

Aralia has the comparative advantage in cars because it sacrifices fewer units of wheat per car. Borland has the comparative advantage in wheat because:

Aralia’s opportunity cost of 1 wheat = 0.25 cars;
Borland’s opportunity cost of 1 wheat = 1/6 car, approximately 0.167 cars.

The central exam point

A country can have an absolute advantage in both products but cannot have a comparative advantage in both products in the standard two-country, two-good model when opportunity costs differ.

The less productive country can still gain from trade by specialising in the product for which its relative disadvantage is smallest.

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Calculating Comparative Advantage

4. Output tables

When a table gives the maximum output possible with the same resources:

opportunity cost of one unit of X = maximum output of Y ÷ maximum output of X

Example:

Country	Coffee	Textiles
C	120	40
D	90	45

Country C

1 textile costs 120 ÷ 40 = 3 coffee.
1 coffee costs 40 ÷ 120 = 1/3 textile.

Country D

1 textile costs 90 ÷ 45 = 2 coffee.
1 coffee costs 45 ÷ 90 = 0.5 textile.

Country D has comparative advantage in textiles because 2 coffee is sacrificed rather than 3. Country C has comparative advantage in coffee because 1/3 textile is sacrificed rather than 0.5.

5. Input-requirement tables

When a table gives the resources or hours needed to produce one unit, a lower input requirement shows absolute advantage. Comparative advantage still requires opportunity-cost calculation.

Suppose:

Country	Hours for 1 unit of software	Hours for 1 unit of food
E	4	2
F	9	3

Country E has absolute advantage in both because it uses fewer hours.

For country E, 4 hours used on software could have made 2 units of food, so the opportunity cost of 1 software is 2 food.

For country F, 9 hours used on software could have made 3 units of food, so the opportunity cost of 1 software is 3 food.

E has comparative advantage in software. F has comparative advantage in food because the opportunity cost of food is lower there:

E: 1 food costs 0.5 software;
F: 1 food costs 1/3 software.

Common calculation trap

Do not select comparative advantage by looking only at the largest output or smallest input number. Always calculate opportunity cost.

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Specialisation and the Gains from Trade

6. Specialisation

Specialisation occurs when a country concentrates more of its resources on producing a narrower range of goods and services.

Under the comparative-advantage model:

lower opportunity cost → specialisation → higher combined output → exchange → consumption possibilities increase

Using the coffee and textiles example:

C specialises more in coffee;
D specialises more in textiles;
combined production can rise because each product is increasingly produced where its opportunity cost is lower.

Specialisation need not be complete in the real world. A country may continue producing some of both goods because of increasing opportunity costs, security concerns, transport costs or the need to diversify.

7. Mutually beneficial terms of trade

The barter terms of trade in a two-good example are the rate at which one product exchanges for another.

For both countries to gain, the international exchange rate must lie between their domestic opportunity costs.

In the coffee-textiles example:

C gives up 3 coffee to make 1 textile;
D gives up 2 coffee to make 1 textile.

A mutually beneficial rate for 1 textile must therefore be between 2 and 3 coffee.

At 2.5 coffee per textile:

C can import 1 textile for 2.5 coffee rather than sacrificing 3 coffee domestically;
D can export 1 textile for 2.5 coffee rather than receiving the equivalent of only 2 coffee domestically.

At exactly one country’s opportunity cost, that country is indifferent and receives no gain from exchange. For both to obtain a positive gain, the rate should lie strictly inside the range.

8. Benefits of specialisation and free trade

Static gains

Higher combined output

Resources are allocated towards lower-opportunity-cost production.

Consumption beyond domestic production possibilities

Trade enables a country to consume combinations it could not produce alone.

Lower prices

Imports can be sourced from lower-cost producers.

Greater consumer choice

Households and firms gain access to products not available domestically.

Access to raw materials and capital goods

Firms can import inputs, machinery and components needed for production.

Dynamic gains

Economies of scale

Access to larger international markets can allow firms to spread fixed costs and use specialised production methods.

Greater competition

Exposure to imports may reduce domestic market power and create incentives to cut costs and innovate.

Technology and knowledge transfer

Imported capital goods, international supply chains and contact with foreign firms can spread production methods.

Investment and growth

Export opportunities can increase expected demand and encourage investment.

These gains are possible, not automatic. Their size depends on adjustment costs, market structure, institutions, infrastructure and the distribution of gains.

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The Trading Possibility Curve

9. Meaning

A production possibility curve (PPC) shows combinations a country can produce using its own resources and technology.

A trading possibility curve (TPC) shows combinations a country can consume after specialising and trading at a given international exchange rate.

The TPC is also described as a consumption possibility line or post-trade consumption line.

10. How to construct and interpret it

A correct diagram should show:

the domestic PPC;
a production point chosen after specialisation;
a trading line passing through that production point;
the slope of the trading line determined by the international terms of trade;
a possible consumption point on the trading line but outside the domestic PPC.

A point outside the PPC is unattainable through domestic production alone. It can become attainable for consumption because exports finance imports.

Essential distinction

The country produces at a point on its PPC and may consume at a different point on its TPC.

Do not say trade shifts the PPC outward. The PPC shifts only if resources, productivity or technology change. Trade expands consumption possibilities without necessarily changing productive capacity.

Why the TPC may not extend consumption possibilities

If the international exchange rate is no better than the country’s domestic opportunity cost, trade produces no gain. Transport costs and tariffs can also reduce or eliminate the effective gain.

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Exports, Imports and the Terms of Trade

11. Meaning of the terms of trade

The terms of trade compare the prices a country receives for its exports with the prices it pays for its imports.

The standard index is:

terms of trade index = (export price index ÷ import price index) × 100

It is a price ratio. It is not:

export volume divided by import volume;
export value divided by import value;
the trade balance;
the current-account balance.

The index is normally expressed relative to a base year, often set equal to 100.

12. Measuring the terms of trade

Suppose:

export price index = 126;
import price index = 120.

Then:

terms of trade = (126 ÷ 120) × 100 = 105

This means the export-price-to-import-price ratio is 5% above its base-year ratio.

Improvement and deterioration

The terms of trade improve when the index rises.
The terms of trade deteriorate when the index falls.

An index above 100 does not necessarily mean the terms of trade are currently improving. It means the ratio is above the base-year ratio. The direction of movement requires comparison with another period.

Example:

Year 1 index = 112;
Year 2 index = 108.

The terms of trade have deteriorated even though the Year 2 index remains above 100.

13. Causes of changes in the terms of trade

The index rises when export prices increase relative to import prices. It falls when import prices increase relative to export prices.

Changes in world demand for exports

Greater demand for a country’s exports may raise export prices and improve its terms of trade, especially if export supply is relatively inelastic.

A fall in world demand may reduce export prices and worsen the terms of trade.

Changes in world supply

A disruption to the world supply of a product a country exports can raise its export price. A global shortage of an imported energy product can raise import prices and worsen the importing country’s terms of trade.

Productivity and production costs

Productivity growth may lower export prices. This can worsen the measured terms of trade while improving competitiveness, export volume and national income. A lower index is therefore not automatically harmful.

Higher domestic costs may raise export prices, but the final effect depends on whether foreign buyers remain willing to buy.

Inflation relative to trading partners

If domestic prices rise faster than foreign prices, export prices may rise relative to import prices. The measured terms of trade might improve, but international competitiveness may weaken and export volume may fall.

Exchange-rate changes

A depreciation often raises the domestic-currency price of imports. It may also change export prices depending on the currency in which contracts are set and how firms adjust their margins. The impact on the terms of trade is therefore not mechanically fixed.

Do not state that depreciation or devaluation must always worsen or improve the terms of trade.

Commodity-price changes

Countries dependent on a narrow range of commodity exports or imports can experience large terms-of-trade movements when world commodity prices change.

14. Impact of an improvement

An improvement means each unit of exports can purchase more imports, other things equal. Possible effects include:

higher real purchasing power from export revenue;
cheaper imported inputs if the improvement comes from lower import prices;
a higher potential standard of living;
lower imported inflation;
increased real national income.

However, the result depends on the cause.

If the improvement comes from a rise in export prices:

foreign demand may fall;
export revenue could rise or fall depending on price elasticity of demand;
export industries may lose output and employment;
domestic firms may become less competitive.

If the improvement comes from falling import prices:

consumers and importing firms benefit;
domestic import-competing firms may face stronger competition.

15. Impact of a deterioration

A deterioration means a given quantity of exports buys fewer imports, other things equal. Possible effects include:

lower real purchasing power;
higher production costs if imported inputs become more expensive;
imported inflation;
pressure on real incomes;
vulnerability for countries reliant on essential imports.

But a deterioration can also accompany stronger export competitiveness if export prices fall because productivity improves. Export volume and employment may rise enough to offset part of the adverse price-ratio effect.

Exam rule

Never conclude from the terms-of-trade index alone that welfare, export revenue or the current account must improve or deteriorate. State the cause, then analyse quantities, elasticities and affected groups.

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Limitations of Absolute and Comparative Advantage

16. Simplifying assumptions

The basic model often assumes:

two countries and two products;
constant opportunity costs;
full employment;
perfect mobility of resources within countries;
no mobility of resources between countries;
no transport or transaction costs;
free trade and no government intervention;
perfect information;
identical product quality;
no external costs or benefits;
fixed technology and resource endowments;
gains can be considered without examining distribution.

These assumptions make the model clear but limit direct real-world application.

17. Adjustment costs and unemployment

Workers, capital and regions cannot always move quickly from contracting import-competing industries to expanding export industries.

Trade liberalisation may therefore create:

structural unemployment;
regional decline;
retraining costs;
stranded capital;
temporary losses of income and tax revenue.

Long-run national gains can coexist with severe short-run losses for particular groups.

18. Increasing opportunity costs

Resources are not equally suited to all activities. As specialisation increases, progressively less suitable resources may be transferred, causing opportunity cost to rise.

This makes complete specialisation less likely and means curved PPCs may be more realistic than straight-line PPCs.

19. Economies of scale and imperfect competition

Comparative advantage is not the only source of trade. Countries with similar resources may trade differentiated products, and large firms may gain from economies of scale.

Market power also matters. A firm or country may capture a large share of the gains, while consumers or suppliers receive less.

20. Externalities, sustainability and strategic concerns

Market prices may omit:

pollution;
carbon emissions;
resource depletion;
labour-standard concerns;
national-security value;
supply-chain resilience.

A country may choose not to specialise fully in a strategically important product even if imports appear cheaper.

21. Dynamic comparative advantage

Comparative advantage can change through:

education and training;
infrastructure;
investment;
technological development;
learning by doing;
industrial policy;
discovery or depletion of natural resources.

Treating current comparative advantage as permanent may trap a country in low-productivity activities. On the other hand, attempting to create a new advantage can waste resources if policy is badly designed.

22. Distribution of gains

A rise in total national income does not mean every person gains.

Possible winners include:

consumers of cheaper imports;
successful exporters;
owners of expanding firms;
workers whose skills are demanded.

Possible losers include:

firms facing import competition;
workers with industry-specific skills;
regions dependent on declining sectors;
groups harmed by environmental effects.

The model shows that gains are possible in aggregate. It does not prove that gains are equal, automatic or politically easy to achieve.

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Full Worked Example

23. Identifying advantage and showing gains

Two countries can use their resources to produce either solar panels or tonnes of rice:

Country	Solar panels	Rice
Lydon	60	120
Merin	30	90

Step 1: Absolute advantage

Lydon can produce more of both products, so it has absolute advantage in both.

Step 2: Opportunity costs

Lydon:

1 solar panel costs 120 ÷ 60 = 2 tonnes of rice;
1 tonne of rice costs 60 ÷ 120 = 0.5 solar panels.

Merin:

1 solar panel costs 90 ÷ 30 = 3 tonnes of rice;
1 tonne of rice costs 30 ÷ 90 = 1/3 solar panel.

Step 3: Comparative advantage

Lydon has comparative advantage in solar panels because 2 rice is less than 3.
Merin has comparative advantage in rice because 1/3 panel is less than 0.5.

Step 4: Mutually beneficial exchange rate

For 1 solar panel, the exchange rate must lie between 2 and 3 tonnes of rice.

At 2.4 tonnes of rice per panel:

Lydon receives 2.4 rice for a panel that costs it 2 rice to produce;
Merin obtains a panel for 2.4 rice rather than sacrificing 3 rice domestically.

Both gain.

Step 5: Diagram interpretation

Each country produces closer to the product in which it has comparative advantage. The trading line through that production point has a slope reflecting 2.4 rice per panel. A consumption point outside the original PPC demonstrates the gain from trade.

Step 6: Evaluation

The predicted gain may be reduced by transport costs, tariffs, rising opportunity costs, unemployment during adjustment or unequal distribution. The model is a benchmark, not a guarantee.

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Exam Mastery

24. Common mistakes

Defining comparative advantage as producing more with fewer resources. That is absolute advantage.
Choosing comparative advantage without calculating opportunity cost.
Assuming the country with absolute advantage in both goods should make both.
Saying trade shifts the PPC outward.
Confusing the trading possibility curve with the production possibility curve.
Calculating terms of trade as import prices divided by export prices.
Treating a terms-of-trade index above 100 as proof it is currently improving.
Confusing terms of trade with the balance of trade.
Assuming an improvement is always beneficial.
Copying past-paper questions or diagrams rather than using original assessment content.

25. Strong analysis chains

Comparative advantage

Country A has a lower opportunity cost of machinery → it specialises more in machinery → Country B specialises more in food → combined output rises → an exchange rate between domestic opportunity costs allows both countries to consume beyond their domestic PPCs.

Terms-of-trade improvement from lower import prices

import prices fall relative to export prices → terms-of-trade index rises → a given quantity of exports buys more imports → imported inputs become cheaper → real income and productive potential may rise, although import-competing firms face stronger competition.

Terms-of-trade deterioration from an energy-price shock

energy import prices rise → import price index rises relative to export price index → terms of trade deteriorate → more exports are needed to finance a given import volume → firms face higher costs and households face lower real purchasing power.

26. Evaluation framework

When evaluating free trade or a change in the terms of trade, ask:

What caused the change?
Is the effect short run or long run?
What are the elasticities of demand and supply?
How mobile are workers and capital?
Are there transport or policy barriers?
Are products homogeneous?
Who gains and who loses?
Are there externalities or strategic concerns?
Can comparative advantage change over time?

A strong conclusion identifies the condition that matters most rather than merely listing advantages and disadvantages.

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Final Summary

Absolute advantage means producing more with the same resources or the same output with fewer resources.
Comparative advantage means producing at lower opportunity cost.
Comparative advantage, not absolute advantage, determines the simple model’s pattern of specialisation.
A mutually beneficial exchange rate lies between the two countries’ opportunity costs.
A trading possibility curve shows post-trade consumption possibilities and may extend beyond the domestic PPC.
Terms of trade = export price index ÷ import price index × 100.
An improvement means the index rises; a deterioration means it falls.
The impact of a terms-of-trade change depends on its cause, elasticities, quantities and distribution.
Free trade can increase output, choice, competition and dynamic efficiency, but adjustment costs and market imperfections matter.
Absolute and comparative advantage are powerful benchmarks, not complete descriptions of real-world trade.