Headline vs core inflation: which one moves the currency?
Why does the market often react more to core inflation than to headline? What does each one leave out, why do central banks watch core, and how far apart did they run in 2026?
Every inflation release arrives as at least two numbers. The headline figure counts everything a household buys, while core leaves out the prices that jump around the most. When the two disagree, the market tends to react more to core, and this post explains why, using the releases of August and September 2026.
What is the difference between headline and core inflation?
Headline inflation is the change in the price of the whole basket. In the US Consumer Price Index (CPI), core is the same basket with food and energy taken out, and calendars list it as its own line, "Core CPI".
Food and energy are a minority of the basket. In the December 2025 weights published by the Bureau of Labor Statistics (BLS), food was 13.7% of the CPI and energy 6.4%, which leaves 79.9% in core.
| Part of the US CPI basket | Weight, December 2025 |
|---|---|
| Food | 13.7% |
| Energy | 6.4% |
| All items less food and energy (core) | 79.9% |
The same split exists in the personal consumption expenditures (PCE) price index, which also comes in a core version that leaves out food and energy.
Why do central banks strip out food and energy?
The reason is persistence, not size. The Fed puts it this way: for food and energy, "a large price change in one period does not necessarily tend to be followed by another large change in the same direction in the following period."
An oil spike can lift headline inflation for a few months and then reverse. Interest rates act with a delay, so a central bank that reacted to every swing in fuel prices would be tightening into a price drop. Core is the closest thing to the trend that policy can still influence.
The goal itself is still written on the full basket. The Fed's 2% target is defined on headline PCE, so core is a guide to where headline is heading, not a replacement for it.
How did the August 2026 US CPI show the difference?
The August CPI, released on 11 September, looked calm on the headline. The annual rate held at 3.4%, according to Action Forex, even though prices rose 0.4% in the month, as expected.
That monthly jump was mostly energy. The energy index swung from a 1.5% fall to a 2.1% rise, and gasoline alone, up 3.9%, made up more than a third of the headline increase.
Core told the other story. The annual core rate eased from 2.5% to 2.4%, but core rose 0.3% in the month against a 0.2% consensus, and the market priced the monthly beat. The probability of a Fed hike at the 16 September meeting went from 72.4% the day before to 88.7%, Action Forex reported, and five days later the Fed delivered that hike, its first since 2023.
| US CPI, August 2026 | Month on month | Year on year |
|---|---|---|
| Headline | 0.4% | 3.4% |
| Energy | 2.1% | 16.3% |
| Core | 0.3% (0.2% expected) | 2.4% |
Two lessons come out of that one release. The monthly core change can move the market more than the annual rate, because it is the newest information. And a headline that matches expectations can hide a core surprise.
How far apart can the two numbers get?
In the oil shock of 2026, a long way. The latest releases from three economies showed a gap of half a point or more, and energy weighed on the headline in all three.
| Release | Headline, year on year | Core, year on year | Gap |
|---|---|---|---|
| US CPI, August | 3.4% | 2.4% | 1.0 point |
| UK CPI, August | 3.1% | 2.6% | 0.5 points |
| Eurozone flash, September | 3.8% | 2.5% | 1.3 points |
The UK figures come from investingLive, which named higher energy prices, led by diesel and petrol, as the biggest contributor. The eurozone figures come from Action Forex: energy inflation jumped from 14.3% to 18.8%, while core edged up from 2.4% to 2.5%, exactly as expected.
Is "core" the same thing in every country?
No, and this is the trap when you compare releases. The eurozone's core leaves out energy, food, alcohol and tobacco. The Japanese core quoted in the release headlines leaves out only fresh food, so it keeps energy in.
Tokyo's September release shows what that changes. Its core rose 2.7%, as our roundup of 3 October reported, while the measure that also leaves out energy reached 3.0%, according to Action Forex. Energy prices in Tokyo were 1.9% lower than a year earlier, so energy was pulling Tokyo's annual rate down rather than up, and the two Japanese "cores" gave different numbers.
Some central banks prefer measures that do not drop any fixed category. The Bank of Canada's CPI-trim cuts "20 per cent of the weighted monthly price variations at both the bottom and top" of the distribution, and its CPI-median takes the price change at the 50th percentile. For August, investingLive reported:
| Canada CPI, August 2026 | Year on year |
|---|---|
| Headline | 3.0% |
| CPI-median | 2.0% |
| CPI-trim | 1.9% |
Three readings of the same month, more than a point apart. Before you react to "core", check which one the release is quoting.
When does core stop being enough?
When the shock lasts. Energy first reaches core through costs, such as transport, and if it persists, wages and the prices firms set start to react to the inflation already seen. Economists call that second step the second-round effect.
The Fed and the European Central Bank (ECB) both hiked through this shock instead of looking past it. The ECB raised its deposit rate to 2.50% on 10 September, and KBC Bank wrote that the ECB's projections keep core inflation well above 2% until 2028. According to KBC, the ECB itself said it did not yet see second-round effects in its wage tracker.
So a gap between headline and core is not a reason to ignore headline. If headline stays far above core for months, the market starts asking when core will follow, and the currency moves on that question.
How should you read the next release?
- Read core month on month first, and compare it to the forecast, not to the previous month.
- Then check the headline. If it diverges, find out whether energy explains the gap.
- Check which core the country uses before comparing two economies.
- Watch the gap over several months. One month with a wide gap is noise; a gap that persists is a risk that core catches up.
What this post does not give you
It does not tell you which way to trade a release. The same core surprise can move a currency in different ways depending on what the market had already priced, and on 11 September, according to Action Forex, the dollar strengthened after the CPI and then gave back most of the move within the session.
It also covers only the measures named above. For how CPI, the Producer Price Index (PPI) and PCE compare as whole indexes, see our guide to the three US inflation measures.
The takeaway
Headline inflation tells you what households paid. Core tells you what the central bank thinks will last, and that is usually what the currency reacts to. In a year of expensive oil the two can sit a full point apart, so read core first, check which core it is, and watch how long the gap stays open.
