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.
Data: U.S. Bureau of Labor Statistics, Consumer Price Index (CPI-U). pumsdata is not affiliated with BLS.
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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 for All Urban Consumers (CPI-U) — verbatim monthly index values from 1997 to the present for the U.S. city average, census regions, and about two dozen metro areas, with percent changes derived from the indexes. pumsdata is an independent product that makes the data easy to chart and compare, and is not affiliated with or endorsed by BLS.