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Consumer Price Index
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CPI Cost Weights Homepage
Background
The Bureau of Labor Statistics (BLS) produces the Consumer Price Index (CPI) as a measure of price change faced by consumers. For use alongside our published indexes, BLS publishes the relative importance (RI) of components in CPI, which is the expenditure weight of an individual component expressed as a percentage of all items within the U.S.
An alternative to using percentages, is to calculate index movements and other related statistics using cost weights, which are additive. For this reason, BLS is publishing on this page cost weights derived from U.S. level all-items totals, available for each weight update back to December 2011. The cost weight for all items is rounded to the nearest hundred million dollars, so that the indexes calculated using these weights will be similar in precision to our officially produced indexes (which are rounded to three decimal places).
A cost weight is an estimated spending total where the price and quantity reference period is different. For example, December 2023 cost weight estimates expenditure totals using prices from December 2023 and quantities from an earlier time period (either 2021 or 2022). To calculate the cost weight for each item category, the all-items cost weight is multiplied by the published relative importance for that category, resulting in an item-level cost weight representing that percentage of the total.
Limitations
The cost weights available on this webpage are calculated outside of the official production system and are at greater risk of calculation errors than the official CPI relative importance. They are intended to be used within one weight update; when crossing a weight revision, it is necessary to pivot to the new weights, or to employ bridging factors. Also note that, just as with the officially published relative importance, due to rounding error these weights do not perfectly sum up to the total. Customers should be aware of the caveats and limitations of any of these products they consider using.
Available data
BLS plans to release annual cost weight data in January, alongside each weight update. Release of this data may be delayed due to resource availability and other constraints.
Data
Related Articles
Information about how to use cost weights to calculate aggregate CPI series is available in the Constructing special Consumer Price Indexes (CPIs) and their percent change factsheet.
Last Modified Date: February 9, 2024