What is being measured
The Consumer Price Index tracks the cost of a basket of things households actually buy, and the release reports how much that cost changed. In the United States it is published monthly by the Bureau of Labor Statistics. Nearly every major economy publishes an equivalent, and the market reaction is the same wherever it lands: the figure is read as pressure on the central bank.
Headline and core
Headline CPI includes everything. Core CPI leaves out food and energy, because those two swing hard for reasons that have nothing to do with the economy overheating — a cold winter or an oil decision is not a reason to raise interest rates. Central banks watch core more closely, which is why a release can move a currency in the direction of the core number even when the headline says the opposite.
Month-on-month and year-on-year
The year-on-year figure compares this month with the same month last year, so it moves slowly and can stay high because of something that happened eleven months ago. The month-on-month figure is the change since last month, so it is noisier but current. When one rises and the other falls, the market usually cares about whichever tells the newer story.
Why the reaction is violent
CPI is the clearest evidence about rates that arrives on a fixed date. Everybody in the market has a position that is right or wrong within one second of the release, so the adjustment is instantaneous. The spread widens beforehand, the first move often reverses, and it is a poor moment to be looking for an entry.
What a surprise actually is
The market has already priced the forecast, so the move comes from the gap between the forecast and the number. A high figure that was expected to be high moves nothing much; an ordinary figure that nobody expected moves a great deal. This is why reading the forecast column matters more than reading the number.
In short
| What it measures | The change in the cost of a basket of household goods |
|---|---|
| Headline | Everything included |
| Core | Food and energy stripped out |
| Watched by | Central banks, closely |
| What moves price | The gap between forecast and figure |
| Frequency | Monthly in most major economies |
Common questions
Why does core matter more than headline?
Because food and energy swing for reasons a central bank cannot fix with interest rates. Core is the part that reflects underlying pressure.
Higher inflation should weaken a currency, so why did it rise?
Because in the short term traders price the central bank’s response. Higher inflation implies higher rates, and higher rates attract money — the textbook effect on purchasing power is a much slower story.
Should I trade the CPI release?
The spread is at its widest and the first move frequently reverses. Waiting for the level the release leaves behind is the version that has a stop worth placing.
Trading forex and CFDs on margin carries a high level of risk. Most retail accounts lose money. Nothing on this page is financial advice or a recommendation to trade.