Key Idea: Your country charges a tariff on imported bicycles. So does the country next door. The two governments agree to drop the tariff on each other's bicycles and keep it on everybody else's. Trade between the two gets easier overnight, and a bicycle from a third country suddenly looks expensive. That is economic integration: countries agreeing to lower the barriers between themselves. The agreements come in stages, each deeper than the last, and each stage hands over a little more control in exchange for a bigger market. The hard question is never whether trade between members rises. It is whether the country ends up buying from the genuinely cheapest producer, or only from the cheapest one inside the club. Where you meet it:
Paper 1
- Essays. This is where the topic is asked.
- Explain [10]: how one stage of integration differs from another.
- Discuss or Evaluate [15]: joining a trading bloc, or joining a monetary union. By far the most common shape here.
Paper 2
- Data response.
- A text describes a country joining a bloc, or a bloc changing its common external tariff.
- Discuss [15] the impact on the member economy, or explain [4] the tariff change using the diagram from 4.2.
Every later trade unit
- The bloc keeps coming back.
- In 4.5 the exchange rate is exactly what a monetary union member gives up.
- In 4.9 a bloc's external tariff is one of the barriers a poorer country outside it faces.
🪜 The ladder of integration
There are five rungs, and each one keeps everything the rung below it had and adds one new thing. The loosest is a preferential trade agreement: members cut the tariffs they charge each other without removing them. Everything above that removes them completely.
| Stage | What it adds to the rung below | A real one |
|---|---|---|
| Preferential trade agreement | members charge each other lower tariffs than they charge anyone else, but the tariffs do not go away | the EU charges lower tariffs on goods from a list of developing countries than on the same goods from anywhere else |
| Free trade area | tariffs and quotas between members go to zero, and each member still sets its own tariff on non-members | USMCA, which replaced NAFTA in 2020, between the USA, Mexico and Canada |
| Customs union | one common external tariff, so every member charges outsiders the same rate | Mercosur, in South America, between Brazil, Argentina, Uruguay and Paraguay |
| Common market | labour and capital move freely between members, as freely as goods do | the EU Single Market, where a nurse trained in one member can work in another without a permit |
| Monetary union | one shared currency and one central bank setting one interest rate for everyone | the euro area, the EU members that share the euro and the European Central Bank |
In a free trade area each member picks its own tariff on outsiders, so an importer can land goods in whichever member charges least and move them on from there. A common external tariff closes that route: same rate everywhere, so it does not matter which member the goods arrive in. You do not need every bloc in the world. Two or three you can name is enough. ASEAN in Southeast Asia and AfCFTA in Africa are both working towards free trade across their members.
🔄 Trade creation and trade diversion
Joining a bloc changes where a country buys things. Sometimes the new supplier is genuinely cheaper to produce from, and the country gains. Sometimes the new supplier only looks cheaper because the tariff has been taken off it, and the country loses. Follow the same country through both.
Trade creation: a gain: Before joining, the country made its own bicycle tyres at **€40** each, and a tariff kept imports out.. Inside the bloc, a member sells the same tyre at **€30**, tariff free. The country stops making tyres and buys them.. The member really is the cheaper producer, so the world uses fewer resources to make the same tyre. The country's buyers pay less.. Production has moved from a **high-cost domestic** producer to a **lower-cost member**. That is trade creation, and it raises welfare..
Trade diversion: a loss: Before joining, the country bought sugar from a **non-member at €20** a sack, the cheapest sugar anywhere.. The bloc's common external tariff of €8 now makes that same sugar cost **€28** inside the country.. A member sells sugar at **€24**, tariff free, so the country switches to the member.. But €24 is what the sugar really costs to produce, against the non-member's €20. The cheapest producer has been shut out by the tariff. That is trade diversion, and it lowers welfare..
Important: After the tariff the member's sugar looks cheapest, at €24 against €28. That is the trap. The country should compare €24 with €20, which is what the two producers actually cost. Getting the two the wrong way round undoes a whole essay. Creation is a gain. Diversion is a loss.
⚖️ Why countries join, and what it costs them
Trade creation is only one of the gains, and trade diversion is only one of the costs. Every 15-mark answer in this topic weighs these two lists, so learn them as a pair.
Why a country joins: **Trade creation.** Production shifts to the cheaper member, so resources are used better.. **A bigger market.** A firm selling to the whole bloc produces more, so its average cost falls. That is economies of scale.. **More competition.** Members' firms now compete with each other, which pushes them to cut costs, innovate and drop prices.. **More foreign investment.** A car maker builds a factory inside the bloc to reach every member's customers tariff free.. **Stronger bargaining.** The bloc negotiates as one, so a small member gets better terms than it would alone..
What membership costs: **Trade diversion.** Imports switch from the efficient outsider to the less efficient member.. **Lost sovereignty.** The member no longer sets its own tariffs, and in a monetary union it gives up its monetary policy too.. **Structural unemployment.** Industries that cannot match a partner's prices close, so those workers lose their jobs and their skills do not fit the jobs that remain.. **Unequal gains.** The larger, richer members usually gain more than the small ones.. **The cost of harmonising rules.** Agreeing one set of standards across many countries is slow and expensive..
Important: The verdict turns on one thing above all: how much of this country's trade is already with the members. If most of it is, the creation is large and the diversion is small, so joining pays. Two more things shift it. A high common external tariff makes diversion worse. Members that produce different things from each other create more trade than members that all produce the same.
💶 One currency, one interest rate
A monetary union is the deepest rung, and the only one that takes a policy tool away. Follow what a member gains, what it hands over, and what happens when trouble arrives in one member and not the others.
What you gain
- No money to change, so trading with another member costs less. No risk that the exchange rate moves between agreeing a price and being paid. Prices are directly comparable across the union, so competition is sharper and firms invest more readily.
What you hand over
- Your own currency and your own interest rate. One central bank now sets one interest rate for every member, and it sets it for the union as a whole.
Then a shock hits one member
- Demand collapses in that member while the others are fine. Its currency cannot fall to make its exports cheaper, because it shares the currency. The shared interest rate is set for the union's average, so it is too high for the member in trouble and about right for everyone else.
So the adjustment lands elsewhere
- On wages, on jobs, and on workers moving to another member to find work. Greece after 2009 could not let its currency fall, so the fall came out of wages and employment instead, while Germany needed no such thing.
The standard case against a monetary union is the one-size-fits-all interest rate. It suits a member whose economy moves in step with the rest of the union, and it does not suit one that does not. So before you answer, ask whether this country would usually need the same interest rate as the other members. If the answer is yes, the cost is small. If its main industry is unlike anyone else's, the lost exchange rate is expensive.
🏛️ Where the WTO fits
Blocs cut barriers between a handful of countries. The World Trade Organization is the body that tries to cut them between all of its members at once, and that sets the rules everyone trades under.
Four things the WTO does
- It sets the rules — The main rule is most-favoured nation: whatever tariff you offer one member, you must offer every member. Trade policy also has to be published, so exporters know what they will face.
- It settles disputes — A member that believes another has broken the rules brings a case instead of hitting back with tariffs of its own. What the WTO cannot do is force a powerful country to obey a ruling.
- It runs rounds of negotiation — Members bargain together to cut barriers across the whole membership. The Doha Round opened in 2001 and stalled, mainly because rich and poorer countries could not agree on farm protection.
- It allows trading blocs — A bloc breaks the equal-treatment rule on purpose: members charge each other nothing and outsiders the full tariff. The rules make room for that, provided the bloc removes the barriers on almost all the trade between its members.
Sets rules → settles disputes → runs negotiations → allows blocs
The WTO's instinct is to treat every member the same. A bloc is discrimination by design: good for insiders, worse for outsiders. Whether the world gains depends on the same test as before, whether creation beats diversion. One more line worth having. Members of a bloc negotiate at the WTO as one, which is why a small country has more say inside a bloc than outside it. The spread of blocs has also meant countries doing deals among themselves instead of waiting for the stalled rounds.
✍️ Worked examples
Four shapes come up in this topic: an Explain that separates two stages, a short data-response Explain with the tariff diagram, and two 15-mark judgements. Try each before opening the plan.
Country X belongs to a free trade area with its neighbours. Its government is considering joining their common market instead. Explain how a free trade area differs from a common market.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Now the short data-response one, where the diagram does half the work.
Text D reports that a customs union has cut its common external tariff on imported washing machines from 20% to 5%. Using a trade diagram, explain the effect of the lower common external tariff on the union's consumers and producers.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Now the judgement that the topic is asked on most often.
A small economy already belongs to a common market, and is deciding whether to adopt the shared currency as well. Using real-world examples, discuss whether a country benefits from joining a monetary union.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
And the mirror image: a member thinking about walking away.
A country has belonged to a customs union for twenty years. A new government argues that leaving would let it set its own tariffs and sign its own trade deals. Using real-world examples, evaluate the case for leaving a trading bloc.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
✅ Quick self-check
Tap each card to check yourself.
What is a preferential trade agreement? The loosest form of integration. Members reduce the tariffs they charge each other without removing them, and charge everyone else the full rate.
What does a customs union add to a free trade area? A common external tariff: every member charges outsiders the same rate. In a free trade area each member sets its own, so goods can be routed in through the member charging least.
What does a common market add to a customs union? Free movement of factors of production. Labour and capital cross between members as freely as goods do.
What does a country hand over in a monetary union? Its own currency, its exchange rate and its monetary policy. It cannot let its currency fall or cut its own interest rate to suit its own circumstances.
Define trade creation. Joining a bloc replaces higher-cost domestic production with lower-cost production from a member. Resources move to where they are used best, so welfare rises.
Define trade diversion. Imports switch from a lower-cost non-member to a higher-cost member, because only the member's goods escape the tariff. Welfare falls.
How do you tell which of the two has happened? Compare the real costs of production, not the prices after the tariff. If the new source is genuinely cheaper it is creation. If it only looks cheaper because the tariff sits on the other one, it is diversion.
Name two things the WTO does. Any two of: sets the rules of trade, including most-favoured nation, which is equal treatment of all members; settles disputes between members; runs rounds of negotiation to cut barriers. It allows trading blocs as an exception to equal treatment.
Exam tips
- Learn the stages in order. Each one keeps everything the stage below it had and adds exactly one thing, so you can rebuild the whole ladder from the bottom.
- The common external tariff is the line between a free trade area and a customs union. That single feature is what the Explain questions test.
- Name a real bloc for the stage you are writing about: USMCA a free trade area, Mercosur a customs union, the EU Single Market a common market, the euro area a monetary union.
- Compare real production costs, not prices after the tariff. That is the only way to tell trade creation from trade diversion.
- Trade creation is a gain, trade diversion is a loss. The wrong way round undoes the whole answer.
- Losing the exchange rate and the interest rate is the standard cost of a monetary union. Name it whenever one comes up, and give the member that needed a different policy from the rest.
- A 15-mark verdict turns on one thing: how much of the country's trade is already with members. Say which way it points instead of writing that it depends.