CPI: monthly movement and annual comparison

Methodological reference; no current numerical release

Research question

Why can monthly inflation slow while a twelve-month reading remains elevated?

BLS publishes index levels and changes over different windows. A one-month change and a twelve-month change describe different comparisons.

A percent change compares the ending index level with the starting level. Use the same index definition at both endpoints.

A recent monthly move is only one part of the annual comparison. Do not treat two different windows as contradictory evidence.

Compare the measurement window with the company’s reporting period before discussing cost pressure or pricing.

This is a methodological note, not a current inflation release or a forecast. No latest CPI figure is asserted.