4.1
Benefits of international trade
Why countries trade: the nine benefits and their mechanisms, the two free-trade diagrams, and at HL comparative advantage, the gains from specialisation and the limits of the theory.
Level and scope checked against the Economics guide (course first assessed 2022; October 2022 update), pp. 20–21, 45–46, on 11 Nov 2026. AI-assisted check, not reviewed by a teacher.
Contents
- 1Learning objectives and review status
- 2HL learning objectivesHL
- 3Why countries trade: nine benefits and how each arises
- 4Free trade on a diagram: importing and exporting at the world price
- 5Who gains and who loses when a market opens
- 6HL: calculating exports, imports, export revenue and import expenditure from a diagramHL
- 7HL: absolute and comparative advantage, and opportunity costs from dataHL
- 8HL: the gains from specialisation and trade, and the sources of comparative advantageHL
- 9HL: limitations of the theory of comparative advantageHL
- 10Common mistakes and exam application
- 11Practice and feedback: 10 marks
- 12Practice and feedback: 10 marks
- 13Practice and feedback: 2 marks
- 14Practice and feedback: 4 marks
- 15Practice and feedback: 4 marksHL
- 16Practice and feedback: 4 marksHL
- 17Practice and feedback: 4 marksHL
- 18Practice and feedback: 10 marksHL
- 19Practice and feedback: 15 marksHL
- 20Sources and review status
1Learning objectives and review status
- Explain, with its mechanism, each of the nine ways in which international trade can benefit a country.
- Draw a free-trade diagram for an imported good and for an exported good, and use it to explain the changes in price, domestic production, domestic consumption and welfare.
- Identify the groups in a country that gain and the groups that lose when one of its markets is opened to trade.
2HL learning objectivesHL only
- Calculate the quantity of imports or exports, import expenditure and export revenue from a free-trade diagram.
- Distinguish absolute advantage from comparative advantage, and calculate opportunity costs from data to identify comparative advantage.
- Use linear production possibilities curves to explain the potential gains from specialisation and trade, and explain where comparative advantage comes from.
- Discuss the limitations of the theory of comparative advantage.
3Why countries trade: nine benefits and how each arises
is the exchange of goods and services across national borders. are goods and services produced in a country and sold to buyers abroad; are produced abroad and bought by the country's residents. is trade with no government-imposed barriers such as tariffs, quotas or subsidies. The of a good is the price at which it is traded on international markets.
Trade changes two things for a country. Its buyers can purchase from the cheapest and most varied sources in the world, not only from domestic firms. Its firms can sell to buyers anywhere, not only at home. Each of the nine benefits below follows from one or both of these changes. Each has a mechanism, and most have a condition under which they are weak.
- 1. Increased competition. When imports enter freely, domestic firms compete with foreign producers as well as with each other. A firm that had few rivals at home can no longer raise its price without losing customers to imports, provided the imported good is a close substitute. To keep its sales it has to cut costs, improve quality or innovate. Consumers and efficient firms gain; inefficient firms lose sales and may close. The effect is weak where the foreign good is a poor substitute or the foreign suppliers are themselves few.
- 2. Lower prices. If the world price of a good is below the price it would have at home without trade, buyers can import it at the world price, so the domestic price falls to that level. Consumers pay less. Firms that use the good as an input have lower costs, which increases the supply of the goods they make. Competition from imports also squeezes domestic firms' profit margins. The fall applies to goods the country imports: the domestic price of a good the country exports rises, as the next section shows.
- 3. Greater choice. Consumers and firms can buy products and varieties that are not made at home: foods that need a different climate, other brands and designs, specialised machinery. Buyers can find something closer to what they want, so their welfare rises even where the average price does not fall.
- 4. Acquisition of resources. No country has every resource. Trade lets a country obtain raw materials, energy, capital goods and technology that it lacks, or could produce only by giving up a great deal of other output. Imported machinery and technology raise the productivity of domestic labour, which increases the economy's productive capacity. The cost is dependence: a country that relies on a few foreign suppliers for essentials is exposed if those supplies are interrupted.
- 5. More foreign exchange earnings. Exports are paid for by buyers abroad, so they earn foreign currency. A country needs foreign currency to pay for its imports, including fuel, medicines and capital goods, and to repay loans taken out in other currencies. This matters most for developing countries, whose own currencies are rarely accepted in payment abroad. Earnings are unstable where exports are concentrated in a few primary commodities, because their prices rise and fall sharply.
- 6. Access to larger markets. A firm that sells only at home is limited by the size of the domestic market, which in a small economy may be too small to support a large plant. Exporting adds foreign buyers to domestic ones. Demand for the firm's output rises, so output, revenue and employment in export industries increase.
- 7. Economies of scale. Producing for a larger market lets a firm raise its output. Where exist, average cost falls as output rises, because the cost of large machinery, research and marketing is spread over more units and inputs can be bought in bulk. Lower unit costs allow lower prices at home and make exports more competitive. The benefit arises only in industries that have not yet used up their economies of scale; it is strongest in manufacturing and for firms based in small economies.
- 8. More efficient allocation of resources. With trade, domestic prices move towards world prices. Industries in which the country is a relatively high-cost producer shrink, because imports are cheaper. Industries in which it is a relatively low-cost producer expand, because they can sell abroad at the world price. Labour and capital move from the first group to the second. The result is : the country concentrates on what it makes at relatively low cost and imports the rest. The same resources then produce output of greater value, so real income rises. This requires that workers and capital can actually move between industries.
- 9. More efficient production. Competition from imports forces each firm to produce at lower cost: less waste, better management, newer methods. Firms can buy cheaper or better inputs and machinery from abroad, and exporters gain economies of scale. Each good is then made with fewer resources.
Benefits 8 and 9 are different points. More efficient allocation is about which goods the country's resources are used for: it is a move towards at world prices. More efficient production is about how each good is made: firms move towards , producing a given output at lower cost.
The benefits do not all arrive at the same speed. Lower prices and wider choice appear as soon as imports reach the shops. Economies of scale, the spread of technology and the movement of resources into expanding industries take years, because they need investment and because workers have to retrain or relocate. In the short run the most visible effect of opening a market may be the contraction of the firms that now compete with imports.
Check your understanding
Key terms
- International trade
- The exchange of goods and services across national borders.
- Exports
- Goods and services produced in a country and sold to buyers in other countries.
- Imports
- Goods and services bought by a country's residents from producers in other countries.
- Free trade
- International trade that takes place without government-imposed barriers such as tariffs, quotas or subsidies.
- World price
- The price at which a good is traded on international markets, which a small economy that trades freely has to accept.
- Economies of scale
- Falls in long-run average cost as a firm increases its scale of output, for example because fixed costs are spread over more units, inputs are bought in bulk, or specialised equipment and labour can be used.
- Specialisation
- Concentrating the resources of a country, firm or worker on producing a narrow range of goods or services.
4Free trade on a diagram: importing and exporting at the world price
Both diagrams show the market for one good in a country that is small in relation to the world market. Small has a precise meaning here: the country's purchases or sales are too little to change the , so it can buy or sell any quantity at that price, Pw. The world supply curve (for a good it imports) or the world demand curve (for a good it exports) is therefore a horizontal line at Pw.
Three further assumptions keep the diagram simple. The foreign good and the domestic good are identical, so buyers care only about price. There are no transport costs. The domestic market is competitive, with domestic demand Dd and domestic supply Sd. Without trade the price is Pe and the quantity Qe, where Dd and Sd cross.
A good the country imports. If Pw is below Pe, buyers can obtain the good more cheaply from abroad. No buyer will pay a domestic firm more than Pw, so the domestic price falls from Pe to Pw. At the lower price the quantity demanded extends along Dd, from Qe to Q2. Domestic firms contract along Sd, from Qe to Q1, because the units they give up cost more than Pw to produce. Domestic production (Q1) is now less than domestic consumption (Q2), and the difference is imported.
The surplus areas show who gains and who loses. rises by the whole area between the two prices out to Dd, because consumers pay less for the units they already bought and buy more units. falls by the area between the two prices out to Sd, because domestic firms sell fewer units at a lower price. The first area is larger than the second by the triangle B-E-J. That triangle is the country's net gain: the units from Q1 to Qe are now obtained from abroad for less than it cost domestic firms to make them, and the units from Qe to Q2 are extra consumption that buyers value above the price they pay. The rectangle under the world price line between Q1 and Q2 is the country's , which is the revenue of foreign producers.
A good the country exports. If Pw is above Pe, domestic producers can sell as much as they wish abroad at Pw, so they will not accept less from buyers at home. The domestic price rises from Pe to Pw. Domestic firms extend along Sd, from Qe to Q2. Domestic buyers contract along Dd, from Qe to Q1. Domestic production (Q2) is now more than domestic consumption (Q1), and the difference is exported.
Here the gains and losses are reversed. Producer surplus rises by the area between the two prices out to Sd; consumer surplus falls by the area between the two prices out to Dd. The producers' gain is the larger by the triangle B-J-E, so the country again gains overall. The rectangle under the world price line between Q1 and Q2 is the country's . The benefit of lower prices therefore applies to the goods a country imports. For a good it exports, domestic buyers pay more than they did without trade.
| World price below Pe | World price above Pe | |
|---|---|---|
| Domestic price | Falls from Pe to Pw | Rises from Pe to Pw |
| Domestic production | Falls from Qe to Q1 (read from Sd) | Rises from Qe to Q2 (read from Sd) |
| Domestic consumption | Rises from Qe to Q2 (read from Dd) | Falls from Qe to Q1 (read from Dd) |
| Trade | Imports of Q2 − Q1 | Exports of Q2 − Q1 |
| Consumer surplus | Rises | Falls |
| Producer surplus | Falls | Rises |
| Country as a whole | Gains triangle B-E-J | Gains triangle B-J-E |
Labels as in the two drawing guides above. In both diagrams Q1 is the smaller quantity and Q2 the larger.
Check your understanding
Check your understanding
Key terms
- World price
- The price at which a good is traded on international markets, which a small economy that trades freely has to accept.
- Imports
- Goods and services bought by a country's residents from producers in other countries.
- Exports
- Goods and services produced in a country and sold to buyers in other countries.
- Consumer surplus
- The total amount consumers are willing to pay above the amount they actually pay, represented by the area below demand and above price.
- Producer surplus
- The total amount producers receive above the minimum amount they would have accepted, represented by the area above supply and below price.
- Import expenditure
- The value of a country's purchases of a good from abroad: the price paid multiplied by the quantity imported.
- Export revenue
- The value of a country's sales of a good abroad: the price received multiplied by the quantity exported.
5Who gains and who loses when a market opens
The net gain on each diagram is a statement about the country's total welfare, not about every person in it. Applying the nine benefits to a real market means asking, for each group, whether the good is one the country imports or one it exports.
| Stakeholder | A good the country imports | A good the country exports |
|---|---|---|
| Domestic consumers | Gain: lower price, more consumed, more choice | Lose in this market: higher price, less consumed |
| Domestic producers of the good | Lose: lower price, output, revenue and profit | Gain: higher price, output and revenue |
| Workers | Jobs are lost in the industry that competes with imports; all workers' wages buy more of the cheaper good | Jobs are created in the export industry |
| Firms that use the good as an input | Gain: lower costs | Lose: higher input costs |
| Government | Lower tax receipts from the shrinking industry; possible spending on support for displaced workers | Higher tax receipts from the expanding industry |
| Foreign producers | Gain sales in this market | Face a new competitor in their own markets |
| The country as a whole | Net gain (triangle B-E-J) | Net gain (triangle B-J-E) |
The gains from an import are spread thinly over a very large number of consumers, each of whom saves a little. The losses are concentrated on particular firms, workers and towns. This is why opening a market is often resisted even when the total gain is positive: the losers know who they are and the winners barely notice.
Whether the gain is realised in full depends on what happens to the resources that the shrinking industry releases. If labour and capital move easily into expanding industries, displaced workers are re-employed quickly and the country reaches the higher level of welfare shown on the diagram. If skills are specific to the old industry, or the industry dominates one region, workers remain out of work for a long time: this is . Part of the gain is then lost, and inequality within the country rises.
Timing matters as well. The losses arrive first and are easy to see. Many of the gains, such as economies of scale, new technology and the growth of export industries, arrive later and are spread across the economy. The diagrams also leave out costs that fall on third parties, such as the pollution from transporting goods over long distances.
Key terms
- Structural unemployment
- Unemployment caused by a mismatch between available jobs and workers' skills, locations or circumstances.
- Consumer surplus
- The total amount consumers are willing to pay above the amount they actually pay, represented by the area below demand and above price.
- Producer surplus
- The total amount producers receive above the minimum amount they would have accepted, represented by the area above supply and below price.
6HL: calculating exports, imports, export revenue and import expenditure from a diagramHL only
When the axes of a free-trade diagram carry numbers, the diagram gives quantities and values. Every answer is built from two readings taken on the world price line: the quantity that domestic consumers demand at the world price Pw, read from the demand curve, and the quantity that domestic firms supply at Pw, read from the supply curve.
- World price below the no-trade price. Quantity of imports = quantity demanded at Pw − quantity supplied at Pw. = Pw × quantity of imports.
- World price above the no-trade price. Quantity of exports = quantity supplied at Pw − quantity demanded at Pw. = Pw × quantity of exports.
- Other values on the same diagram. Domestic producers' revenue = Pw × quantity supplied. Domestic consumers' expenditure = Pw × quantity demanded. Before trade, both equal the no-trade price multiplied by the no-trade quantity.
- Functions instead of a grid. If the question gives demand and supply functions, substitute Pw into each to find the two quantities, then proceed in the same way.
- Units. Quantities carry the unit on the horizontal axis (for example thousand tonnes); revenue and expenditure are in currency. A price in dollars multiplied by a quantity in thousands gives thousands of dollars.
Check your understanding
Key terms
- Import expenditure
- The value of a country's purchases of a good from abroad: the price paid multiplied by the quantity imported.
- Export revenue
- The value of a country's sales of a good abroad: the price received multiplied by the quantity exported.
- World price
- The price at which a good is traded on international markets, which a small economy that trades freely has to accept.
- Imports
- Goods and services bought by a country's residents from producers in other countries.
- Exports
- Goods and services produced in a country and sold to buyers in other countries.
7HL: absolute and comparative advantage, and opportunity costs from dataHL only
Absolute advantage and comparative advantage answer different questions. A country has an in a good if it can produce more of it than another country with the same quantity of resources, or the same output with fewer resources. A country has a in a good if it can produce it at a lower than another country. Opportunity cost here is the quantity of the other good that must be given up to produce one more unit of this good.
The model has two countries and two goods. In each country resources can be switched from one good to the other at a constant rate, so each production possibilities curve (PPC) is a straight line and the opportunity cost is the same at every point on it.
The theory of comparative advantage states that if opportunity costs differ between two countries, total output is higher when each specialises in the good in which its opportunity cost is lower and trades for the other. This holds even when one country has the absolute advantage in both goods. Being more productive at everything is not a reason to make everything: resources that the more productive country uses for the good in which its lead is smaller could have produced more value in the good in which its lead is larger.
- Output data. The table gives the most of each good that a country can produce with the same resources. Opportunity cost of one unit of X = maximum output of Y ÷ maximum output of X. The good being costed goes underneath.
- Input data. The table gives the resources, such as hours of labour, needed to make one unit of each good. Opportunity cost of one unit of X = input needed for one X ÷ input needed for one Y: the hours used for one X could have made that many units of Y. With input data a smaller number means higher productivity.
- Say which kind of data the table holds before calculating. Applying the output method to input data inverts every answer.
- The two costs in one country are reciprocals. If 1 cloth costs 2 wheat, then 1 wheat costs 0.5 cloth. It follows that if one country has the lower opportunity cost in X, the other has the lower opportunity cost in Y. A country cannot have the comparative advantage in both goods.
- Equal opportunity costs. If the cost of X in terms of Y is the same in both countries, the PPCs are parallel, neither country has a comparative advantage and the model predicts no gain from specialisation.
- Write the conclusion with its reason and its units. For example: X has the comparative advantage in cloth because 1 cloth costs it 2 wheat, less than the 4 wheat it costs Y.
Check your understanding
Key terms
- Absolute advantageHL
- The ability of a country to produce more of a good than another country from the same quantity of resources.
- Comparative advantageHL
- The ability to produce a good at lower opportunity cost than another producer or country.
- Opportunity cost
- The value of the next best alternative forgone when a choice is made; it is the loss from not pursuing that alternative.
8HL: the gains from specialisation and trade, and the sources of comparative advantageHL only
The arise in two steps. The first is : each country moves resources into the good in which it has the comparative advantage. Resources are then used where their opportunity cost is lowest, so the two countries together can produce more of at least one good without producing less of the other, provided that resources stay fully employed and can move between the two industries. The second step is exchange: the countries trade at a rate that lies between their two opportunity costs, so each obtains the good it no longer makes for less than it would cost to produce at home. Each country can then consume a combination of goods that lies outside its own PPC.
| Country X: cloth | Country X: wheat | Country Y: cloth | Country Y: wheat | Total cloth | Total wheat | |
|---|---|---|---|---|---|---|
| Production and consumption without trade | 20 | 20 | 5 | 20 | 25 | 40 |
| Production with specialisation | 30 | 0 | 0 | 40 | 30 | 40 |
| Consumption after X exports 8 cloth for 20 wheat | 22 | 20 | 8 | 20 | 30 | 40 |
All figures are invented. They continue the output-data worked example: X can produce 30 cloth or 60 wheat, Y can produce 10 cloth or 40 wheat.
The rate at which the goods are exchanged must lie between the two opportunity costs. Country X will not sell cloth for less than 2 wheat per unit, because it can obtain 2 wheat for each unit of cloth it gives up simply by growing wheat itself. Country Y will not pay more than 4 wheat per unit of cloth, because it can make cloth itself at that cost. Any rate between 2 and 4 leaves both countries better off. In the table the rate is 2.5 wheat per cloth. A rate close to 2 gives most of the gain to Y; a rate close to 4 gives most of it to X.
Opportunity costs differ between countries because their resources differ. A country's are the quantities and qualities of the factors of production it has. A country tends to have its comparative advantage in goods that use its abundant factor intensively.
- Land and natural resources. Fertile land, minerals and energy reserves give a low opportunity cost in farming, mining and the industries that process their output.
- Labour. A large labour force with low wages gives a comparative advantage in labour-intensive manufactures such as clothing. A highly educated labour force gives one in goods and services that need specialised skills.
- Capital. A large stock of machinery, factories and infrastructure favours capital-intensive goods such as vehicles and chemicals.
- Climate and geography. Tropical crops need a tropical climate. Natural harbours and closeness to large markets lower the cost of supplying those markets.
- Technology and accumulated know-how. Spending on research and long experience in an industry lower its costs relative to those of other countries.
Comparative advantage is not fixed. Investment in education, infrastructure and technology changes a country's factor endowments and, with them, its opportunity costs, so a country can move over time from labour-intensive exports to goods that need more capital and skill. Government policy can therefore help to create a comparative advantage, which is the starting point of the infant industry argument for protection.
Check your understanding
Key terms
- Gains from tradeHL
- The increase in total output and in each country's consumption possibilities that results when countries specialise according to comparative advantage and trade.
- Specialisation
- Concentrating the resources of a country, firm or worker on producing a narrow range of goods or services.
- Factor endowmentsHL
- The quantities and qualities of land, labour, capital and enterprise that a country possesses, which shape its opportunity costs.
- Comparative advantageHL
- The ability to produce a good at lower opportunity cost than another producer or country.
- Production possibilities curve
- A model showing the maximum combinations of two outputs that can be produced with given resources and technology, assuming efficient use.
9HL: limitations of the theory of comparative advantageHL only
The theory draws a strong conclusion, that every country gains by specialising according to its comparative advantage, from a very simple model. Each limitation below is a point at which an assumption of the model differs from reality, together with what that difference does to the conclusion.
- Two countries and two goods. In reality there are many of each. The principle still applies, but the model cannot say which of thousands of goods a country will export, and complete specialisation in one good is not observed.
- Constant opportunity costs. In reality resources are not equally suited to every use, so the opportunity cost of a good rises as more of it is produced and specialisation stops before it is complete. In industries with economies of scale the opposite happens: costs fall as output grows, so the country that starts first can keep the industry whatever its endowments.
- Resources move freely between industries and stay fully employed. In reality workers may lack the skills that the expanding industry needs, or live in the wrong region. Specialisation then causes structural unemployment, so part of the predicted gain is not realised and the losses fall on particular groups.
- No transport costs. In reality transport, insurance and delay can be larger than a small difference in costs, above all for bulky goods of low value. Some goods are not traded even though opportunity costs differ.
- Free trade and perfect competition. In reality tariffs, subsidies and firms large enough to set prices distort the prices at which goods are traded, so the pattern of trade need not follow opportunity costs.
- Identical goods and perfect knowledge. In reality products are differentiated and buyers do not know every source of supply. Countries with similar costs both export and import varieties of the same product, which the theory does not explain.
- The theory is static. It takes today's opportunity costs as given. A country that specialises in what it is relatively good at today, for example a low-value primary product, may never build the industries in which productivity grows fastest. The gain now can be paid for with slower growth later.
- Over-specialisation. The model treats specialisation as free of risk. A country that depends on a narrow range of exports exposes its income, employment and government revenue to a fall in the world price, a change of policy by a trading partner, crop disease or natural disaster.
- Distribution and third parties. The gain is a gain to the country as a whole. The theory says nothing about who receives it, nothing about the environmental costs of production and transport, and nothing about a country's wish to be self-sufficient in strategic goods such as food or energy.
Check your understanding
Key terms
- Comparative advantageHL
- The ability to produce a good at lower opportunity cost than another producer or country.
- Specialisation
- Concentrating the resources of a country, firm or worker on producing a narrow range of goods or services.
- Factor mobility
- The ease with which land, labour, capital or enterprise can move between alternative uses.
- Structural unemployment
- Unemployment caused by a mismatch between available jobs and workers' skills, locations or circumstances.
10Common mistakes and exam application
11Practice and feedback: 10 marks
12Practice and feedback: 10 marks
13Practice and feedback: 2 marks
14Practice and feedback: 4 marks
15Practice and feedback: 4 marksHL only
16Practice and feedback: 4 marksHL only
17Practice and feedback: 4 marksHL only
18Practice and feedback: 10 marksHL only
19Practice and feedback: 15 marksHL only
20Sources and review status
Written with AI assistance. The sources below were consulted on ; each entry says what it was used for and what it does not cover. Not reviewed by a teacher. Not approved as a finished revision resource.
Not yet checked against any source: the benefits of trade other than competition, economies of scale and the transfer of knowledge (taken from the guide's list); the free-trade diagram for an exported good; the sources of comparative advantage and the limitations of the theory as lists.
Sources consulted
Diploma Programme Economics guide (course first assessed 2022; October 2022 update; cover reads "First assessment 2024")
International Baccalaureate. IB curriculum document, learner's own copy, 10 Nov 2026. Printed pp. 20-21 (syllabus outline) and the topic tables on the printed pages recorded on each syllabus node; assessment outline pp. 60-65; command terms pp. 74-75. PDF page = printed page + 6.
Used for: Topic titles, the scope of each topic and SL/HL level, the assessment format and the command terms, as recorded on each syllabus node.
Limits: Read from the learner's own PDF, which is not redistributed. The IB's online copy could not be opened by automated access (HTTP 403 on 11 November 2026), so this copy was not compared with it. It sets what must be taught; it does not explain the economics. AI-assisted reading, not checked by a teacher.
Principles of Microeconomics 3e: 19.4 The Benefits of Reducing Barriers to International Trade
OpenStax, Rice University. Reference, read in full, 11 Nov 2026. Section 19.4
Used for: Tariffs as taxes on imports; gains from trade through economies of scale, competition and the transfer of knowledge.
Limits: Does not define nontariff barriers on this page. University-level US textbook: its wording, examples and diagrams are not IB wording and it is not an authority for IB scope or SL/HL level.
Global Trade Outlook and Statistics, March 2026 (news item, 19 March 2026)
World Trade Organization. Real-world source, read in full, 11 Nov 2026. News item text, headline figures
Used for: 2025 merchandise trade volume growth, 2026–27 forecasts, AI-related goods share, MFN share of world trade
Limits: 2025 figures are preliminary (data as of 10 March 2026) and subject to revision; forecasts exclude a prolonged energy shock scenario.
Principles of Microeconomics 3e: 20.1 Protectionism: An Indirect Subsidy from Consumers to Producers
OpenStax, Rice University. Reference, read in full, 11 Nov 2026. Section 20.1
Used for: Protectionism, tariffs, import quotas and nontariff barriers; a demand-and-supply analysis showing that trade barriers raise the domestic price, raise domestic output and reduce consumption; who gains and who pays.
Limits: Does not mention tariff revenue, quota rent, welfare-loss triangles or export subsidies. University-level US textbook: its wording, examples and diagrams are not IB wording and it is not an authority for IB scope or SL/HL level.
International Trade: Theory and Policy, 7.8 Import Tariffs: Small Country Welfare Effects
Saylor Academy (open textbook). Reference, read in full, 11 Nov 2026. Chapter 7, section 7.8, Table 7.3
Used for: A tariff in a small importing country: consumer surplus falls by A+B+C+D, producer surplus rises by A, government revenue rises by C, and national welfare falls by B+D, the production and consumption efficiency (deadweight) losses.
Limits: Open textbook published by Saylor Academy in 2012 under CC BY-NC-SA 3.0 with the author's name withheld at the author's request; undergraduate level.
Principles of Microeconomics 3e: 3.5 Demand, Supply, and Efficiency
OpenStax, Rice University. Reference, read in full, 11 Nov 2026. Section 3.5
Used for: Definitions of consumer surplus, producer surplus and social (total) surplus; deadweight loss; the inefficiency of price floors and ceilings.
Limits: Definitions and diagrams only; no worked surplus-triangle calculations. University-level US textbook: its wording, examples and diagrams are not IB wording and it is not an authority for IB scope or SL/HL level.
The World Bank in Viet Nam: Overview
World Bank. Real-world source, read in full, 11 Nov 2026. Context section
Used for: Đổi Mới 1986; GDP per capita under $500 (1986) to $5,066 (2025); trade-to-GDP nearly 190%; poverty at $4.20/day; upper-middle-income reclassification July 2026
Limits: Country overview written by a development partner; undated page (most recent items September 2026). The page calls the $4.20/day figure 'extreme poverty' although $4.20 is the lower-middle-income line.
Human Development Report 2025, Statistical Annex Tables 1–7
United Nations Development Programme. Real-world source, read in full, 11 Nov 2026. Tables 1 (HDI), 2 (trends), 3 (IHDI), 5 (GII); country rows named in each claim
Used for: HDI, components, GNI per capita, IHDI and GII values and ranks for 2023
Limits: Data year is 2023. Read from pdftotext (raw mode) extraction; values cross-checked between Tables 1, 2 and 3. Superseded when HDR 2026 is released (1 December 2026).
Principles of Microeconomics 3e: 19.1 Absolute and Comparative Advantage
OpenStax, Rice University. Reference, read in full, 11 Nov 2026. Section 19.1
Used for: Definitions of absolute and comparative advantage; opportunity costs computed for two countries; gains from specialisation and trade in a worked numerical example.
Limits: Labour-hours example; no terms of trade. University-level US textbook: its wording, examples and diagrams are not IB wording and it is not an authority for IB scope or SL/HL level.
OpenStax, Rice University. Reference, read in full, 11 Nov 2026. Section 19.2
Used for: A country with an absolute advantage in every good still gains from trade by specialising according to comparative advantage; linear production possibility frontiers; the range of exchange ratios at which both countries gain.
Limits: Two-country, two-good model with constant opportunity costs. University-level US textbook: its wording, examples and diagrams are not IB wording and it is not an authority for IB scope or SL/HL level.
Understanding the WTO: The case for open trade
World Trade Organization. Reference, read in full, 11 Nov 2026. Section on comparative advantage
Used for: Comparative advantage attributed to David Ricardo; a country that is worse at producing everything still gains by specialising in what it does relatively best.
Limits: Advocacy for open trade by the WTO; it does not present the arguments for protection.
The World Bank in Bangladesh: Overview (updated 25 October 2026)
World Bank. Real-world source, read in full, 11 Nov 2026. Context section
Used for: Second-largest exporter of ready-made garments; lower-middle-income status; poverty estimated to have risen for a fourth consecutive year; FY27 growth projection 3.4%
Limits: No export-share figure on the page.
United Nations LDC Portal (UN DESA). Real-world source, read in full, 11 Nov 2026. Status summary
Used for: Graduation from LDC status rescheduled to 24 November 2029 after a General Assembly resolution of 29 October (2026)
Limits: The page does not print the year of the 29 October resolution; 2026 is inferred from context and news coverage.
USTR Takes Action in Forced Labor Section 301 Investigations (press release, July 2026)
Office of the United States Trade Representative. Real-world source, read in full, 11 Nov 2026. Whole release
Used for: Section 301 action of 23 July 2026: tariff tiers (10% / 12.5%), list of 17 economies at 10%, exemption categories
Limits: Government press release; effective date and product annex are in the Federal Register notice, which was not opened (site redirected to a block page).