Methodology · Consumer Price Index
Seasonal adjustment(SA/NSA)
Removing predictable calendar swings from a series — and why annual rates use NSA data while monthly rates use SA.
Some price movements repeat every year on schedule: gasoline rises into summer driving season, apparel goes on clearance after the holidays. Seasonal adjustment (SA) statistically removes those predictable patterns so that consecutive months can be compared — a seasonally adjusted increase means prices rose beyond what the calendar alone would predict. The unadjusted series (NSA) is the raw record of what prices actually did.
The two series divide the work by convention, which BLS and pumsdata both follow: year-over-year changes are computed from the NSA index, because comparing the same month a year apart already cancels seasonality; month-over-month changes are computed from the SA index, because otherwise every January would look like deflation. Not every series has an SA version — many metro-area and detailed-item series are published NSA-only, which is why some pages show no month-over-month figure.
Also known as: SA, NSA, seasonally adjusted, not seasonally adjusted.
Data: U.S. Bureau of Labor Statistics, Consumer Price Index (CPI-U). pumsdata is not affiliated with BLS.
See seasonal adjustment in the data
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Seasonal adjustment — FAQ
What is seasonal adjustment in inflation data?+
Removing predictable calendar swings from a series — and why annual rates use NSA data while monthly rates use SA. Some price movements repeat every year on schedule: gasoline rises into summer driving season, apparel goes on clearance after the holidays. Seasonal adjustment (SA) statistically removes those predictable patterns so that consecutive months can be compared — a seasonally adjusted increase means prices rose beyond what the calendar alone would predict. The unadjusted series (NSA) is the raw record of what prices actually did.
Why does seasonal adjustment matter?+
The two series divide the work by convention, which BLS and pumsdata both follow: year-over-year changes are computed from the NSA index, because comparing the same month a year apart already cancels seasonality; month-over-month changes are computed from the SA index, because otherwise every January would look like deflation. Not every series has an SA version — many metro-area and detailed-item series are published NSA-only, which is why some pages show no month-over-month figure.
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.