Currency movements are reported daily with confident explanations, and the actual drivers are more varied and less immediately observable.
Interest rate differentials
Capital moves toward higher expected returns.
Which makes relative interest rate expectations a primary driver.
What matters is the change relative to what was already expected rather than the level.
Expectations rather than events
Markets price anticipated developments in advance.
Which is why a rate rise that was expected produces little movement.
The surprise component is what moves prices, and this explains many apparently counterintuitive reactions.
Trade and current account
Persistent imbalances affect currency demand over longer periods.
Which operates slowly relative to capital flows.
Short-term movements are dominated by financial rather than trade flows.
Safe haven flows
Certain currencies appreciate during periods of uncertainty regardless of domestic conditions.
Which reflects their role in the international financial system.
This can move a currency against what domestic economic news would suggest.
Purchasing power parity
The theory that exchange rates should equalise the price of comparable goods.
Which holds poorly in the short run and has some support over long periods.
Deviations persist for years, which limits its practical use.
Intervention
Central banks buying or selling their own currency.
Which is used in some jurisdictions and generally has limited lasting effect without supporting policy.
Coordinated intervention has historically been more effective than unilateral action.
Effects of a weaker currency
Imports become more expensive and exports more competitive.
Which passes into consumer prices with a lag.
Pass-through is incomplete and varies by economy and by product.
Reading currency coverage
Explanations attributing a day's movement to a single cause are generally speculation.
Trends over months are more interpretable than daily moves, and central bank communications explain more than commentary does.
Carry trades
Borrowing in low-yielding currencies to invest in higher-yielding ones.
Which can move currencies substantially and unwinds abruptly during risk events.
These unwinds have produced some of the sharpest currency movements on record.
Pegged and managed regimes
Some currencies are fixed or managed against others.
Which requires reserves and policy alignment to maintain.
Peg breaks are historically dramatic and have followed sustained pressure on reserves.
Reserve currencies
Currencies held internationally for trade and reserves.
Which produces persistent demand independent of the issuing economy's performance.
Composition of global reserves is published and changes slowly.
For travellers and businesses
Forward contracts and hedging manage exposure for businesses with foreign currency commitments.
Which is standard practice and is worth understanding for anyone with meaningful exposure.
For travellers, comparing the all-in rate including spread and fees is the practical exercise.
Sources worth reading
Central bank statements and minutes explain policy direction more reliably than market commentary.
Political events
Elections, referendums and policy announcements move currencies where they change expectations about policy.
Which is why the reaction depends on what was already priced in.
Markets frequently move before events on anticipated outcomes and reverse when those outcomes differ.
Commodity currencies
Economies dependent on resource exports see currencies move with commodity prices.
Which is a reasonably stable relationship.
It transmits global commodity cycles into domestic prices and fiscal positions.
Inflation differentials
Higher relative inflation tends to weaken a currency over time.
Which is the mechanism behind long-run purchasing power arguments.
The relationship is weak over short periods and stronger over decades.
Foreign exchange market structure
The largest financial market by volume, operating continuously across time zones.
Which means liquidity varies by session and affects execution.
Practical implications
For most people currency matters through import prices and travel costs rather than directly.
Why daily explanations are usually wrong
Many factors move simultaneously and the market prices expectations rather than events.
Which means attributing a single day's movement to a single cause is generally narrative rather than analysis.
Over months, the drivers become identifiable and the story becomes more reliable.
A final observation
Currency markets price expectations about future policy, and the news that moves them is the news that differs from what was already expected.
Once that is understood, most apparently perverse reactions to economic data become straightforward.
Where to look for reliable analysis
Central bank publications, international financial institution reports and academic work on exchange rate determination.
Which are considerably more measured than daily market commentary and are freely available.
The honest position in the academic literature is that short-horizon exchange rate movements are extremely difficult to explain, let alone predict.
The practical summary
Interest rate expectations dominate short-run movement, trade and inflation differentials matter over years, and daily explanations are mostly narrative.
One more thing worth knowing
Retail currency exchange carries a spread that dwarfs the movements discussed in market coverage.
Which means for most people the difference between a good and a bad exchange rate is a matter of where they change money rather than what the market did that week.
Comparing the all-in rate, including any fee, is the entire exercise.