An exchange counter displays a number: so many rupees for one dollar, or so many dollars for one euro. Who chose it? In many cases, no single person did. It reflects a market in which banks, businesses, investors and others buy and sell currencies.
But not every currency follows the same arrangement. Some float relatively freely, some are managed and some are pegged to another currency or basket. The answer begins with the system a country uses.
A currency has a price in another currency
An exchange rate is a relative price. If one unit of currency A buys more of currency B than before, A has appreciated against B. The opposite movement is depreciation.
That relative nature matters. A currency can strengthen against one counterpart and weaken against another at the same time. A broad index comparing several trading partners can therefore tell a different story from a single bilateral rate.
At the retail counter, fees and a buying-selling spread also affect the quote. The rate a traveller receives is not necessarily the wholesale market rate seen on a financial screen. They describe related transactions at different levels of the market.
Why demand changes
Businesses need currencies to pay for imports and receive export earnings. Investors need them to purchase assets abroad. Expectations about future returns and risk influence where that money goes.
Interest-rate differences can matter because they change the relative appeal of interest-bearing assets. All else equal, higher returns may attract funds, but “all else equal” is a substantial qualification. Concerns about inflation, default or political risk can outweigh the attraction of a higher stated rate.
Trade prices matter too. The Reserve Bank of Australia explains how commodity prices and export earnings can influence demand for Australian dollars. Other economies have different export mixes, so the same commodity shock need not affect every currency in the same way.
Where central banks enter
A floating rate does not mean a central bank has no influence. Its interest-rate decisions can change financial conditions and expectations. It may also buy or sell foreign currency under its policy framework.
A peg involves a stronger commitment to a particular rate or range. Maintaining it can require reserves, policy adjustments or other measures when market pressure develops. Announcing a desired number does not remove the economic forces acting on it.
The distinction between a target and a market outcome is useful. Authorities can shape the system and intervene, but sustaining a rate involves costs and constraints rather than simply editing a price label.
Why predictions are difficult
Exchange rates respond to new information, including information about what people expect other people to do. A widely anticipated policy change may already be reflected in prices before the official announcement.
A stronger currency can make imports cheaper while making exports more expensive to foreign buyers; a weaker one can reverse those pressures. The effects vary across households and businesses.
So who decides a currency’s worth? Depending on the regime, policy sets part of the framework and countless transactions fill in the moving price. The number is a live relationship between economies, not a permanent grade awarded to a country.