Exchange rates: why a currency rises or falls

Last summer your £100 bought 120 of a country’s coins at the airport kiosk. This summer the same £100 buys only 108. Nothing about your money changed — the notes in your wallet are identical. What changed is the price of one currency in the other. That price has a name — the exchange rate — and like every price you’ve met in this course, it is set by supply and demand. Once you see what’s pushing on it, the airport board stops being a mystery and starts being a message.

An exchange rate is just a price

Back in the price lesson, you saw that a price is two crowds leaning against each other — buyers wanting more, sellers offering more — settling on one number. A currency is no different. It has a price, and that price is how much of another currency one unit of it buys.

Here is the part people miss. To buy a country’s goods, its property, or its bonds, you almost always have to buy its currency first. A factory in one country can’t pay its workers in your money. So when the world wants more of a country’s stuff, the world must first buy more of its currency — and demand for that currency goes up. When the world wants less, demand falls.

That single fact carries the whole lesson. The currency is wanted not for itself, but as the ticket you need before you can buy anything inside that country.

What pushes a currency up

Four crowds reach for a country’s currency, and each one lifts its price.

People who want its exports. A carmaker abroad sells brilliant cars. Buyers everywhere need that country’s currency to pay for them. More buyers of the cars means more buyers of the currency.

Foreigners investing there. Someone wants to build a factory, or buy shares, or own property in that country. They must convert their money into the local currency first. A flood of investment is a flood of demand for the currency.

Savers chasing higher interest rates. You met the interest-rate thermostat earlier in the course. Raise a country’s key rate and its banks and bonds pay savers more. Money is mobile — savers around the world move their cash to where it earns most. To park money there, they buy that currency. Higher rates pull money in and lift the currency.

Confidence and safety. When the world is frightened, money runs to currencies it trusts to hold value. Calm, stable, predictable — that reputation alone pulls buyers in.

Reverse any of these and the currency sinks. Exports lose their shine, investors pull out, the central bank cuts rates, or trust cracks — and now everyone is selling the currency, swapping back into something else. More sellers than buyers, and the price drops.

A worked example: the rate moves

Say one Home-pound buys 1.10 Abroad-dollars. Demand on both sides is balanced; the rate sits still.

Now Home invents something the world suddenly wants — a machine everyone must have.

1. Buyers abroad want the machine. To pay for it, they first need Home-pounds.
2. They show up at the currency market holding Abroad-dollars, all trying to buy Home-pounds.
3. More buyers chasing the same pounds. By the rule of every price, the pound’s price rises.
4. The rate climbs from 1.10 to 1.20 — one Home-pound now buys 1.20 Abroad-dollars.

The pound got stronger. Nobody decreed it. The extra demand for Home’s machine became extra demand for Home’s currency, and the price followed.

Run it the other way. Home’s central bank cuts its interest rate to near zero. Savers earn almost nothing there, so they move their money abroad where it pays more.

1. To leave, they sell their Home-pounds and buy Abroad-dollars.
2. Sellers of pounds now outnumber buyers.
3. The pound’s price falls — say from 1.10 down to 1.00.

The pound got weaker. A rate cut sent money out, and selling the currency pushed its price down. (You’ll feel both directions in the lab — toggle each force and watch the rate tip.)

Why “strong” isn’t simply “good”

It’s tempting to cheer a rising currency and dread a falling one. Resist that. A weaker currency is not a defeat — it’s a trade-off, and which side of it you’re on decides whether it helps or hurts.

When Home’s pound weakens, Home’s exports get cheaper for the rest of the world. The same car now costs foreign buyers less, so they buy more of it. Home’s exporters and the people they employ do better. Inbound tourists find Home cheap and pour in.

But the same weak pound makes everything Home imports more expensive — foreign oil, foreign phones, the holiday a Home family takes abroad. Importers and outbound travellers do worse.

So a falling currency lifts the exporter while it squeezes the importer. A rising one does the reverse. There is no setting that is gentle on everyone at once.

The whole, not the kiosk

Step back from the airport board. That one number is a meeting point for billions of separate choices — a manufacturer’s sale, a saver moving cash, a tourist booking a flight, a fund deciding where it trusts its money. None of them coordinated. None of them could see the others. Yet their pushes and pulls settle into a single price that then quietly reshapes who can afford what, an ocean away.

And you are inside it, not above it. The same move that makes a stranger’s exports cheaper makes your holiday dearer; the rate that rewards a saver across the world is the rate that nudged your £100 down to 108 coins. You sit on one side of every currency move — sometimes the side it lifts, sometimes the side it squeezes — and almost never the side that chose it. Worth holding loosely, then, the instinct to call any rate “good.” It is good for someone, and that someone may not be you.