Core inflation, headline inflation, and why economists prefer the number that ignores food
Excluding the things people actually buy sounds absurd. There is a reason for it, and there is a real criticism of it.
Headline inflation measures the price change of everything in the basket. Core inflation excludes food and energy. To anyone who buys food and energy this seems like a strange thing to prefer.
The reason for excluding them
Food and energy prices are volatile and are driven by factors that have nothing to do with the domestic economy: weather, harvests, geopolitics, production decisions taken by a cartel.
A central bank is trying to detect whether inflation is becoming embedded, meaning built into wage bargaining and pricing decisions. A spike in oil after a supply disruption tells it nothing about that, and reacting to it would mean tightening into a shock that is already reversing.
Core is therefore a better signal of the underlying trend, which is what policy can actually influence.
The criticism, which is fair
Nobody experiences core inflation. Households experience headline. If food and energy rise persistently, dismissing them as volatile is a statistical convenience that diverges from lived experience, and that divergence corrodes trust in the institution doing the dismissing.
There is also a substantive version of the objection: sustained energy costs feed into the price of everything transported or manufactured, so a long-running energy shock eventually shows up in core anyway. Treating it as noise can mean acting late.
The measures worth knowing
- Headline: everything. What people experience.
- Core: excludes food and energy. The policy signal.
- Trimmed mean: discards the largest movers in both directions rather than fixed categories.
- Core services excluding housing: the wage-sensitive slice central bankers currently watch most closely.
The last of those has been the most-quoted measure of this cycle, because it is the part of inflation most tied to the labour market and therefore the part policy reaches most directly.
How to read an inflation headline
Look at the monthly change, not just the annual one. The annual rate includes eleven months of history and can fall purely because a large increase a year ago has dropped out of the window. The monthly number tells you what is happening now.
This is general education and not investment advice.
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