Measures · Consumer Price Index
Year-over-year inflation
The percent change in the index from the same month a year earlier — the standard 'inflation rate'.
Year-over-year (y/y) inflation is the percent change in a price index from the same month one year earlier: 100 × (this month's index ÷ the same month last year's index − 1). It is computed from index levels, not published separately — an index that moves from 310.0 to 320.9 over twelve months is 3.5% y/y inflation. By convention it is calculated from the not-seasonally-adjusted (NSA) index, because comparing the same calendar month a year apart already nets out seasonal patterns. That is how BLS states the headline annual rate, and how every y/y figure on pumsdata is derived.
Two reading disciplines matter. First, a falling y/y rate does not mean falling prices: going from 6% to 3% means prices are still rising, just more slowly — prices actually fell only when the y/y number is negative. Second, when a month is missing from the record (October 2025, when the federal shutdown halted collection), any 12-month pair touching the hole is skipped rather than estimated — the missing month is never interpolated.
Also known as: y/y, annual inflation rate, 12-month change, inflation rate.
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Year-over-year inflation — FAQ
What is year-over-year inflation in inflation data?+
The percent change in the index from the same month a year earlier — the standard 'inflation rate'. Year-over-year (y/y) inflation is the percent change in a price index from the same month one year earlier: 100 × (this month's index ÷ the same month last year's index − 1). It is computed from index levels, not published separately — an index that moves from 310.0 to 320.9 over twelve months is 3.5% y/y inflation. By convention it is calculated from the not-seasonally-adjusted (NSA) index, because comparing the same calendar month a year apart already nets out seasonal patterns. That is how BLS states the headline annual rate, and how every y/y figure on pumsdata is derived.
Why does year-over-year inflation matter?+
Two reading disciplines matter. First, a falling y/y rate does not mean falling prices: going from 6% to 3% means prices are still rising, just more slowly — prices actually fell only when the y/y number is negative. Second, when a month is missing from the record (October 2025, when the federal shutdown halted collection), any 12-month pair touching the hole is skipped rather than estimated — the missing month is never interpolated.
Where does this inflation data come from?+
All figures come from the U.S. Bureau of Labor Statistics Consumer Price Index. pumsdata is an independent product and is not affiliated with the BLS.