IB Economics SLTopic 4 — The Global EconomyPaper 1 & 2Core idea~8 min read
Monetary Union
A monetary union is the last step on the ladder. Members already trade freely, already share an external tariff, already let people and money move. Now they share a currency and a central bank as well, which means giving up the two tools a country normally uses when things go wrong.
📘 What you need to know
A monetary union has everything a common market has, plus a common central bank, a single currency and one monetary policy for all members.
The clearest example is the euro area, where around twenty of the twenty-seven EU members use the euro.
Being in the EU does not mean being in the euro. Denmark keeps its own currency, and the UK never joined the euro before it left the EU.
Gains: no exchange rate risk inside the union, lower transaction costs, prices easy to compare, more cross-border trade and investment, and the credibility of a large independent central bank.
Costs: no independent interest rate, no exchange rate to adjust with, and fiscal rules on deficits and debt.
One interest rate must suit every member, which is a problem when their economies are at different points in the cycle.
A union works best when members have similar business cycles, mobile labour and some way of transferring money to a member in trouble.
The central trade-off
Everything about monetary union comes back to one exchange: certainty in return for flexibility. You know exactly what your exports will earn in a partner’s market, forever. In return, when your economy alone gets into trouble, you have almost nothing left to pull.
The credibility point is worth remembering. A member with a history of high inflation borrows the reputation of the union’s central bank, which can lower its borrowing costs.
WORKED EXAMPLE
A firm sells 5,000,000 euros of goods a year into the union and currently pays 1% in currency conversion and hedging costs. Calculate its annual saving from joining. [2]
Step 1: what the cost is now1% × 5,000,000 = 50,000 euros a yearStep 2: what it becomes inside the union
With one currency there is nothing to convert, so the cost falls to zero.
A saving of 50,000 euros a yearSmall percentages on large flows are how the transaction cost argument adds up across a whole economy. Say that in an essay rather than just calling the saving “significant”.
One interest rate, different economies
This is the strongest criticism, and the one worth drawing. The central bank sets a single rate for the whole union, based on average conditions. If your economy is not average, that rate is wrong for you, and there is nothing you can do about it.
Economists call this an asymmetric shock: something that hits one member and not the others. Inside a union there is no interest rate and no exchange rate left to answer it with.
Outside a union, a country in trouble can cut rates and let its currency fall, which makes its exports cheaper and brings demand back. Inside one, the adjustment has to come out of wages and jobs instead, which is slower and far more painful. That single comparison is the best evaluation sentence on this page.
What makes a union work
Since members cannot adjust with interest rates or exchange rates, something else has to do that job. Three conditions matter, and they are exactly what to test a proposed union against.
Condition
Why it matters
What happens without it
Similar business cycles
One rate can suit everyone at once
The rate is wrong for somebody all the time
Mobile labour
Workers move from weak regions to strong ones
Unemployment stays stuck where the shock landed
Fiscal transfers
Money can flow to a member in trouble
The member must cut spending in a downturn
Similar productivity trends
Competitiveness does not drift apart
Some members slowly price themselves out
Why fiscal rules exist. If one member borrows recklessly and gets into difficulty, the whole currency is affected, so unions set limits on deficits and debt. The awkward result is that the rules bite hardest in a recession, exactly when a government would normally want to spend.
WORKED EXAMPLE
Plan: “Evaluate the benefits for a small open economy of joining a monetary union.” [15]
1 Set-up
Define a monetary union. Note that “small open economy” matters: a large share of its output is traded, so exchange rate risk is a big deal for it.
2 The case for
Exchange rate uncertainty disappears with its main trading partners; transaction costs fall; investors face less currency risk; a credible central bank can bring lower inflation and cheaper borrowing.
3 The case against
Interest rates are set for the union average, not for this economy; no devaluation available if it loses competitiveness; fiscal rules limit the response to a downturn; adjustment falls on wages and employment instead.
4 What it depends on
Does its cycle move with the union’s? Can workers move? Are there transfers when a shock hits? How much of its trade is with members?
5 Judgement with a reason
“For a small economy whose trade is mostly with the union and whose cycle moves with it, the gains are likely to outweigh the costs. For one whose main exports are different from the union’s, the loss of an independent interest rate is a serious risk that shows up precisely when it is least affordable.”
Two conditions decide the verdictNotice the conclusion answers for two different types of economy rather than sitting on the fence. That is what a context-aware judgement looks like.
💡 Exam tip
Define it as a stack: customs union plus common market plus a single currency and central bank.
Name the two lost tools separately. The interest rate and the exchange rate are different instruments and both go.
Use the phrase “asymmetric shock” and then explain it in plain words. Term plus explanation scores twice.
Say which trading partners matter. The gains rise with the share of trade done inside the union.
Split the timing. Gains are steady and small; costs are rare and large. Good evaluation notices that.
Do not confuse EU membership with euro membership. Examiners notice, and it is an easy fact to get right.
⚠️ Common mix-up
Thinking a common market means a shared currency. It means factors of production move freely, nothing more.
Saying members lose fiscal policy. They keep it, but within agreed limits on deficits and debt.
Assuming one currency removes all price differences. It makes them visible, which is not the same as removing them.
Treating the loss of the exchange rate as minor. For a country that has lost competitiveness, it is the main issue.
Listing benefits with no conditions. The union suits members whose economies move together, and hurts those that do not.
Forgetting that joining is a political decision too. Sovereignty is part of the cost even when the economics is favourable.
Up next: Floating Exchange Rates — what happens to a currency when nobody is holding it in place, and the demand and supply diagram that explains it.
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