Macro & Liquidity
CPI Explained: How the Inflation Gauge Works
Last updated 2026-07-23
The Consumer Price Index (CPI) measures the average change in prices paid by consumers for a representative basket of goods and services, published monthly by the U.S. Bureau of Labor Statistics. Its year-over-year change is the most widely quoted measure of inflation; 'core' CPI strips out volatile food and energy prices to show the underlying trend.
Why it matters to investors
Inflation is the variable central banks are mandated to control, so CPI releases move rate expectations — and through them, bond yields, equity valuations, and the dollar — more than almost any other data print.
Sustained inflation also changes the investing regime: real (inflation-adjusted) returns, not nominal ones, are what compound wealth, which makes the inflation trend a core input for long-horizon allocation.
How to read it
- Watch core CPI and its month-over-month pace for the trend; headline CPI for what households actually experience.
- Note that the Federal Reserve's 2% target is defined on a different index — PCE inflation — which typically runs a few tenths below CPI.
- Compare the inflation trend to policy rates: a positive real policy rate (rates above inflation) is restrictive; deeply negative real rates are stimulative.
Data sources: U.S. Bureau of Labor Statistics · FRED (CPIAUCSL, CPILFESL)
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Common questions
What is the difference between CPI and PCE inflation?
Both track consumer prices, but PCE (Personal Consumption Expenditures) uses a broader basket that updates weights more dynamically, and it is the index the Federal Reserve's 2% target is defined on. CPI typically prints slightly higher than PCE.
Why do markets react to core CPI more than headline?
Food and energy prices are volatile and often driven by supply shocks central banks cannot control. Core CPI filters that noise, so it is the better guide to the underlying inflation trend policy responds to.