IB Economics SLTopic 4 — The Global EconomyPaper 1 & 2Core idea~9 min read
Trading Blocs and How They Differ
A trading bloc is a group of countries that agree to trade more freely with each other. The three types are not separate ideas; they are the same idea at increasing depth, each one adding something the last did not have. Get the ladder straight and this topic becomes very easy marks.
📘 What you need to know
A trading bloc is a group of countries that reduce or remove barriers between themselves, making trade cheaper and easier.
A free trade area removes barriers between members, but each member keeps its own barriers against outsiders.
A customs union adds a common external tariff, so all members charge outsiders the same rate.
A common market adds free movement of the factors of production, so labour and capital can move between members.
Each step means giving up more sovereignty over your own trade policy.
Trade creation is the gain: cheaper members’ goods replace dearer domestic production.
Trade diversion is the loss: trade shifts away from an efficient outsider towards a less efficient member, just because the member’s goods are tariff free.
Whether a bloc is good for a country depends on which of those two effects is larger.
The ladder of integration
The European Union is a customs union and a common market, and most of its members also share a currency. A free trade area such as the North American agreement stops at the first step.
Type
Barriers between members
Barriers against outsiders
Factors of production
Free trade area
Removed
Each member sets its own
Stay put
Customs union
Removed
One common external tariff
Stay put
Common market
Removed
One common external tariff
Move freely
Monetary union
Removed
One common external tariff
Move freely, one currency
Here is the detail that impresses examiners. Because members of a free trade area keep different external tariffs, goods could sneak in through whichever member charges least and then move on tariff free. So free trade areas need rules about where a product was really made. A customs union does not need them, because the outside tariff is the same everywhere.
Trade creation and trade diversion
Joining a bloc does two opposite things at once, and the whole evaluation of trading blocs sits in the balance between them. One makes the country better off; the other makes it worse off; the numbers decide which wins.
In both cases the consumer pays less after joining. Only in the first case is the country actually better off, because only there did the good become genuinely cheaper to produce.
WORKED EXAMPLE
Under a 15% per unit tariff of $15, a country imports from an outside supplier at $80 before tariff. A bloc partner can supply at $90. The country joins a customs union with the partner. Show the effect per unit. [4]
Step 1: before joining
Outsider costs 80 + 15 = $95; partner costs 90 + 15 = $105. The country buys from the outsider at $95.
Step 2: after joining
The partner pays no tariff, so it sells at $90, which beats the outsider’s $95. Trade is diverted.
Step 3: who gains and who loses per unitconsumer: 95 − 90 = +$5government: loses the $15 tariff it used to collectnet: +5 − 15 = −$10Step 4: sense check with real costs
The good used to take $80 of resources to make; now it takes $90. Same answer: a loss of $10.
The country is $10 per unit worse offThe tariff was never a cost to the country, only a transfer from buyers to the government. That is why the consumer’s saving does not settle it.
Weighing blocs up
In favour
Against
A bigger market allows economies of scale
Loss of sovereignty over trade policy
Trade creation raises efficiency
Trade diversion can outweigh it
More employment where members specialise
Industries that cannot compete shrink fast
Stronger bargaining power in world talks
Members must negotiate as a group, not alone
Closer political ties and cooperation
Outsiders face discrimination, which invites disputes
Free movement of labour fills skill gaps
Regions can lose workers to richer members
The exam-ready judgement: a bloc is more likely to help when its members were already each other’s natural trading partners, and more likely to divert trade when the efficient supplier is sitting outside the wall.
💡 Exam tip
Say what each step adds, not just what it is. “A customs union is a free trade area plus a common external tariff” is one clean sentence.
Define trade creation and diversion by direction: creation moves production to a cheaper source, diversion moves it to a dearer one.
Compare resource costs, not prices with tariffs added. Tariffs are transfers inside the country.
Name a bloc for each type so your examples are precise rather than “the EU” every time.
Use sovereignty in evaluation. It is a real cost even when it does not show up in a calculation.
For 15-mark answers, end on the balance: which effect is larger, and what that depends on.
⚠️ Common mix-up
Free trade area versus customs union. The difference is only the external tariff, and that is the mark.
Thinking trade diversion means less trade. Trade often rises; it just comes from a less efficient source.
Judging by the consumer price alone. Diversion can lower the price and still make the country worse off.
Calling a common market a monetary union. Free movement of factors does not mean a shared currency.
Assuming a bloc is automatically good. The net effect is an empirical question, not a definition.
Forgetting outsiders. Every bloc makes somebody’s exports less competitive by design.
Up next: Monetary Union — the deepest step of all, where countries give up their own interest rate and their own exchange rate at the same time.
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