Inflation and Forex

Inflation moves currencies because it determines what central banks do with interest rates, and interest rates determine the return from holding a currency. A higher-than-expected inflation reading raises the likelihood of tighter policy and tends to strengthen the currency in the short term; a lower-than-expected reading does the reverse. The relationship runs through the policy response, which is why the same inflation number can have opposite effects depending on how the central bank is expected to react.

What inflation is

Inflation is the rate at which the general level of prices rises over time. Statistical agencies measure it by tracking the cost of a representative basket of goods and services and reporting the change, usually monthly and year over year.

Most central banks target a specific inflation rate, and their mandates require them to steer inflation toward it. When inflation runs above target, the bank is expected to tighten policy by raising rates or reducing asset purchases. When it runs below, the bank is expected to ease. The central banks and currency markets article describes this framework.

Two channels to the currency

Inflation affects a currency through two mechanisms that can pull in different directions.

The policy channel

Higher inflation prompts expectations of higher interest rates. Higher expected rates attract capital and strengthen the currency. This channel dominates over short horizons, and it is why a strong inflation print typically produces an immediate rise in the currency.

The purchasing-power channel

Over longer horizons, a currency that experiences persistently higher inflation than its peers loses purchasing power relative to them. Goods priced in that currency become more expensive, trade competitiveness erodes, and the exchange rate tends to adjust downward to compensate. This is the logic of purchasing-power parity, which holds loosely over years but not over weeks.

The two channels explain an apparent contradiction: high inflation can strengthen a currency in the short run while weakening it in the long run. Which effect dominates depends on whether the central bank is expected to respond credibly.

Which measures matter

The US CPI is the most market-moving single inflation release globally, because it arrives early in the month and because the dollar is on one side of most trades. The PCE index arrives later and is usually less surprising, since much of it can be inferred from CPI and PPI, but it is the measure the Federal Reserve references for its target.

Headline versus core

Headline inflation includes every item in the basket. Core inflation strips out the most volatile components, typically food and energy, to reveal the underlying trend.

Central banks generally focus on core measures because they want to respond to persistent pressures rather than to temporary swings in commodity prices. A headline print driven by a spike in petrol prices may not change policy if core inflation is stable. A core print above expectations is more likely to shift rate expectations, and therefore the currency, than a headline surprise of the same size.

Within core inflation, policymakers increasingly distinguish between goods and services. Services inflation, and especially measures that exclude housing, is often treated as the best indicator of domestically generated price pressure linked to wages. The employment data and forex article explains why wage growth and inflation are analysed together.

Reading an inflation release

The market reaction to an inflation print depends on the difference between the reported figure and the consensus forecast, not on the figure itself.

These are tendencies, not rules. The reaction also depends on where the central bank is in its cycle. A hot print when the bank is already expected to raise rates confirms the path and may move little. The same print when the bank has signalled a pause forces a repricing and moves a great deal.

Inflation expectations

Central banks watch not only realised inflation but expectations of future inflation, because expectations influence wage demands and pricing behaviour. Measures include surveys of consumers and businesses, and market-based measures derived from the gap between nominal and inflation-protected bond yields.

A rise in inflation expectations can move a currency even without a change in realised inflation, because it implies that the central bank will need to do more. Conversely, well-anchored expectations give a central bank room to look through temporary spikes.

Inflation, real rates, and other markets

Inflation interacts with the interest-rate framework through real rates, the nominal rate minus inflation. A rise in inflation that is not matched by a rise in nominal rates lowers real rates, which tends to weigh on the currency over time and to support assets such as gold. A rise in nominal rates that outpaces inflation raises real rates and tends to support the currency.

The interest rates and forex article covers this relationship. Commodity prices, particularly oil, feed into headline inflation directly through energy and transport costs, which is one reason energy shocks complicate central-bank decisions.

Practical considerations

Inflation releases are scheduled and appear in the economic calendar. The moments around a US CPI release are among the most volatile of the month for dollar pairs, with spreads widening and slippage common. Positions held through the release should be sized from a stop distance that accounts for this, using the position size calculator.

A useful habit is to note the consensus forecast for both headline and core before the release, and to read the reaction against those numbers rather than against the previous month's figure.

Key takeaways

• Inflation moves currencies through the expected central-bank response; a hot print raises rate expectations and tends to strengthen the currency in the short term.
• Over long horizons, persistently high inflation erodes purchasing power and tends to weaken a currency, so the short- and long-run effects can differ.
• Core inflation, and increasingly services inflation, matters more for policy than headline, because central banks respond to persistent rather than volatile pressures.
• US CPI is the most market-moving inflation release globally; PCE is the Federal Reserve's target measure.
• The reaction depends on the surprise relative to consensus and on where the central bank is in its cycle, not on the absolute figure.
• Inflation expectations, real rates, and commodity prices all feed into how markets interpret an inflation release.