๐๏ธ Session 5: Free trade โ blessing or curse?
Abstract
This session examines trade: the classical case for free trade, from Smith and Ricardo, and the challenges to it โ unequal terms of trade, technological lock-in, and the externalization of ecological costs across countries. The environmental conflicts this produces on the ground were planned for the second half, but moved to the next session for lack of time (see Environmental conflicts, Session 6).
๐ฅ๏ธ Lecture Slides
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- Link to the Tweedback Session
1. Adam Smith: absolute advantage (slides 8โ9)
The setup. Germany ๐ฉ๐ช and Japan ๐ฏ๐ต each have 100 units of labour (L). If a country uses all of its labour on one good, it can produce:
| L | ๐ฅจ (all labour) | ๐ฑ (all labour) | |
|---|---|---|---|
| ๐ฉ๐ช | 100 | 20 | 10 |
| ๐ฏ๐ต | 100 | 16 | 12 |
From this follows how much labour one unit of each good costs:
- ๐ฉ๐ช: one ๐ฅจ costs \(100/20 = 5\) L, one ๐ฑ costs \(100/10 = 10\) L.
- ๐ฏ๐ต: one ๐ฅจ costs \(100/16 = 6.25\) L, one ๐ฑ costs \(100/12 \approx 8.33\) L.
So ๐ฉ๐ช is absolutely better at pretzels (5 L < 6.25 L) and ๐ฏ๐ต is absolutely better at bento (8.33 L < 10 L). Each country has an absolute advantage in one good.
Relative value. The last column of the slideโs left table shows what one pretzel is worth within each country, measured in bento. In ๐ฉ๐ช, the labour for one ๐ฅจ (5 L) could instead produce half a ๐ฑ (\(5/10 = 0.5\)). In ๐ฏ๐ต, the labour for one ๐ฅจ (6.25 L) could produce \(6.25/8.33 = 0.75\) ๐ฑ. Equivalently, divide the two production possibilities: \(10/20 = 0.5\) and \(12/16 = 0.75\).
No trade. Without trade, each country must produce both goods itself. The slide assumes that each country splits its labour evenly, 50 L per good:
- ๐ฉ๐ช: \(50/5 = 10\) ๐ฅจ and \(50/10 = 5\) ๐ฑ
- ๐ฏ๐ต: \(50/6.25 = 8\) ๐ฅจ and \(50/8.33 = 6\) ๐ฑ
- World (๐บ๐ณ): \(10 + 8 = 18\) ๐ฅจ and \(5 + 6 = 11\) ๐ฑ
Trade. Now each country puts all its labour into the good in which it has the absolute advantage: ๐ฉ๐ช makes 20 ๐ฅจ and no ๐ฑ; ๐ฏ๐ต makes 12 ๐ฑ and no ๐ฅจ. World output rises to 20 ๐ฅจ and 12 ๐ฑ, which is 2 ๐ฅจ and 1 ๐ฑ more than before. Not a single extra hour was worked: the gain comes entirely from the division of labour.
| No trade ๐ฅจ | No trade ๐ฑ | Trade ๐ฅจ | Trade ๐ฑ | Change ๐ฅจ | Change ๐ฑ | |
|---|---|---|---|---|---|---|
| ๐ฉ๐ช | 10 | 5 | 20 | 0 | +10 | โ5 |
| ๐ฏ๐ต | 8 | 6 | 0 | 12 | โ8 | +6 |
| ๐บ๐ณ | 18 | 11 | 20 | 12 | +2 | +1 |
The corridor in which both win (slide 9). Specialisation alone leaves ๐ฉ๐ช without bento and ๐ฏ๐ต without pretzels, so the two have to exchange. Suppose ๐ฉ๐ช sends \(x\) ๐ฅจ to ๐ฏ๐ต and receives \(y\) ๐ฑ in return. Each country should end up with more of both goods than it had without trade:
- ๐ฉ๐ช keeps \(20 - x\) ๐ฅจ, which must exceed 10, so \(x < 10\); and it receives \(y\) ๐ฑ, which must exceed 5, so \(y > 5\).
- ๐ฏ๐ต receives \(x\) ๐ฅจ, which must exceed 8, so \(x > 8\); and it keeps \(12 - y\) ๐ฑ, which must exceed 6, so \(y < 6\).
Hence \(8 < x < 10\) and \(5 < y < 6\). This is the slideโs corridor: ๐ฉ๐ช trades roughly 8.1โ9.9 ๐ฅจ for 5.1โ5.9 ๐ฑ. Within it, the \(+2\) ๐ฅจ and \(+1\) ๐ฑ of extra world output are shared between the two countries, and how they are shared depends on where in the corridor the exchange lands.
Note how the corridor lines up with the relative values: the implied exchange rate \(y/x\) lies between \(5/10 = 0.5\) and \(6/8 = 0.75\) bento per pretzel. That is, the price at which the two countries trade must lie between their two domestic relative values. Below 0.5, ๐ฉ๐ช would be better off making bento itself; above 0.75, the same holds for ๐ฏ๐ต and pretzels.
2. David Ricardo: comparative advantage (slides 10โ12)
The setup. This is Ricardoโs original example. The table now shows labour requirements, i.e. how many hours it takes to produce one unit:
| ๐ท (wine) | ๐งฅ (cloth) | |
|---|---|---|
| ๐ต๐น | 80 | 90 |
| ๐ด๓ ง๓ ข๓ ฅ๓ ฎ๓ ง๓ ฟ | 120 | 100 |
Portugal needs fewer hours for both goods, so it has an absolute advantage in both. On Smithโs logic there would be no reason to trade. Ricardo shows that there is one anyway.
Who is relatively better at what (slide 11). Compare Portugalโs labour requirements with Englandโs, good by good:
- ๐ท: \(80/120 \approx 0.67\), so Portugal needs only 67% of Englandโs labour.
- ๐งฅ: \(90/100 = 0.9\), so Portugal needs 90% of Englandโs labour.
Portugalโs lead is much larger in wine, so its comparative advantage lies in ๐ท, and Englandโs (its smallest disadvantage) in ๐งฅ.
Opportunity costs. The same result follows from asking what each country gives up. The 90 hours Portugal spends on one ๐งฅ could instead produce \(90/80 = 1.125\) ๐ท. In England, the 100 hours for one ๐งฅ could instead produce \(100/120 \approx 0.833\) ๐ท. So cloth is relatively cheaper in England (it costs 0.833 ๐ท there versus 1.125 ๐ท in Portugal), and by the same token wine is relatively cheaper in Portugal (it costs \(80/90 \approx 0.89\) ๐งฅ there versus \(120/100 = 1.2\) ๐งฅ in England). Note that what matters is not how many hours a good takes in absolute terms, but how much of the other good one must forgo to produce it.
No trade (slide 12). Suppose each country produces one unit of each good:
- ๐ด๓ ง๓ ข๓ ฅ๓ ฎ๓ ง๓ ฟ: \(120 + 100 = 220\) hours for 1 ๐ท and 1 ๐งฅ
- ๐ต๐น: \(80 + 90 = 170\) hours for 1 ๐ท and 1 ๐งฅ
- World: 2 ๐ท and 2 ๐งฅ
Specialisation. Now each country uses the same hours only for the good in which it has the comparative advantage:
- ๐ต๐น: \(170/80 = 2.125\) ๐ท and no ๐งฅ
- ๐ด๓ ง๓ ข๓ ฅ๓ ฎ๓ ง๓ ฟ: \(220/100 = 2.2\) ๐งฅ and no ๐ท
- World: 2.125 ๐ท and 2.2 ๐งฅ, which is 0.125 ๐ท and 0.2 ๐งฅ more with the same total labour of 390 hours.
The terms of trade. As in Smithโs case, the two countries must exchange. Suppose England sends 1 ๐งฅ to Portugal and receives \(w\) ๐ท in return:
- ๐ด๓ ง๓ ข๓ ฅ๓ ฎ๓ ง๓ ฟ ends up with \(2.2 - 1 = 1.2\) ๐งฅ and \(w\) ๐ท. It is better off than before if \(w \geq 1\).
- ๐ต๐น ends up with 1 ๐งฅ and \(2.125 - w\) ๐ท. It is better off than before if \(2.125 - w > 1\), so \(w < 1.125\).
Any exchange of 1 ๐งฅ for between 1 and 1.125 ๐ท thus leaves both countries with more than they had without trade. More generally, the price of cloth must lie between the two opportunity costs from above: above Englandโs 0.833 ๐ท (otherwise England would rather make its own wine) and below Portugalโs 1.125 ๐ท (otherwise Portugal would rather make its own cloth).
The take-away. Trade can be mutually beneficial even when one country is more productive in everything. What drives the gains are differences in opportunity costs, not in absolute productivity. This simple narrative remains at the core of many trade debates and analyses, which is why it is worth looking closely at the assumptions built into it: full employment, labour as the only input, no transport costs, and no ecological costs of production or shipping.
๐ Data sources for the figures
Every data figure in the lecture is built from openly available data. The table below says where each one comes from, so you can check a claim from the lecture and, more importantly, pull the same data for your own country.
| Figure in the lecture | Where the data come from |
|---|---|
| South Korea: GDP per capita compared with other regions | Maddison Project Database 2023 (Bolt and van Zanden 2025), via Our World in Data |
| South Korea: exports by product group, 1962โ2024 | Atlas of Economic Complexity (The Growth Lab at Harvard University 2026b), exports by SITC section |
| Solar PV module prices vs. cumulative installed capacity | Our World in Data (Our World in Data 2026), combining Nemet (2009), Farmer and Lafond (2016) and IRENA |
| Solar PV module production by country, 2024 | IEA-PVPS (2025), as reported by pv magazine. Entered by hand, as there is no download |
| The terms-of-trade problem | The Grilli-Yang commodity price index, 1900โ2016 (Pfaffenzeller et al. 2007), in the version of Geronimi et al. (2018), extended with the World Bank Pink Sheet (World Bank 2026) |
| The countryโproduct matrix (who exports what) | Atlas of Economic Complexity, all countries ร 4-digit products (HS 1992), 2024 |
| The product space | Layout and links from the Growth Labโs product space network (The Growth Lab at Harvard University 2026a); node sizes from Atlas trade data |
| The product space for three country groups | As above, combined with the Atlas data for every country |
๐งญ Economic complexity for your country
The figures on technologically unequal exchange all come from the Atlas of Economic Complexity of the Harvard Growth Lab. You do not need any code to use it for your poster:
- Country profiles: start here. For your country they show what it exports, how the export basket has changed since the 1960s, its rank in the Economic Complexity Index, and which products lie โnearbyโ in the product space.
- Explore: treemaps, trade partners, the product space with your countryโs exports highlighted, and time series, all downloadable.
- Rankings: economic complexity and the Growth Labโs growth projections.
- Data downloads: the full underlying data, if you want to compute something yourself.
Three concepts from the lecture that you will meet there:
- Revealed comparative advantage (RCA). A country has RCA โฅ 1 in a product if that product makes up a larger share of the countryโs exports than it does of world trade. The countryโproduct matrix in the lecture marks exactly these cells.
- Diversity and ubiquity. Diversity is the number of products a country exports with RCA โฅ 1; ubiquity is the number of countries that export a given product with RCA โฅ 1. The Economic Complexity Index combines the two (Hidalgo 2021).
- The product space links two products when countries tend to export both with RCA โฅ 1. Your countryโs position in it shows which new products are within reach of the capabilities it already has (Hidalgo et al. 2007).
A caveat to carry into the poster: economic complexity describes the productive structure of an economy. It tells you nothing about whether that structure is ecologically sustainable or socially just. Look at what your country exports and at what this extraction or production costs on the ground, which is where Session 6 picks up.
Every figure above is built by two R scripts, trade_01_download.R (fetches the data) and trade_02_figures.R (draws the figures). They live in the analysis/ folder of the course repository, together with a README that explains how to run them and how to fetch Atlas data for your own country with a few lines of R. You are welcome to change a country, a year or a colour, or to lift the approach for your own poster.
- Look at data on your countryโs trade and trade openness.
- Complement this with data on its export composition, its economic complexity, and its position in the product space.
- What is your country specialised in? How has this changed over time?
- What are the prospects for the future: which products lie within reach, and how does this relate to the key challenge you have identified?
- How much does the current policy mix take into account capability constraints?
๐ Up-front Reading
Please read before the session:
- Chapters 18 and 19 in Daly and Farley (2011).
๐ Follow-up Reading
- Kolcava et al. (2019)