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Consumer Price Index

Recent and upcoming methodology changes: 2023

Changes to used cars and trucks methodology (updated February 13, 2024)

With the release of January 2024 data, the CPI program updated the mileage adjustment applied to each sampled used vehicle in the used cars and trucks index. Historically, a single, stable mileage amount estimated for a given make and model was applied to each sampled vehicle and remained unchanged throughout the year. The assigned mileage amount is now replaced with a monthly average mileage amount based on the age of the sampled used vehicle, and not the make and model. Each estimated price for a sampled used vehicle is still adjusted for depreciation.

In addition, seasonally adjusted indexes as well as calculated seasonal adjustment factors will take the new methodology into account beginning in 2024. Revised seasonal factors are available at Seasonal Adjustment in the CPI.

Details on the new method are available on the Measuring Price Change in the CPI: Used cars and trucks factsheet.

Changes to health insurance methodology (posted August 22, 2023)

Following recommendations from the National Academies of Science, Engineering, and Medicine’s Committee on National Statistics (CNSTAT), the BLS is improving the methodology used to calculate retained earnings in the CPI health insurance index. Under the pre-October 2023 method, retained earnings were updated annually, without any smoothing of the data. Under the new methods, the BLS will update retained earnings every six months using half-year data and will calculate a two-year moving average to smooth the changes in retained earnings. The update in November 2023 (publication of October 2023 data) involved a 6-month transition using annual data that has been averaged (smoothed) over two years. In May 2024 (publication of April 2024 data), we will begin to incorporate half-year, rather than annual, retained earnings. After this date, the retained earnings will be updated every six months with April and October data which will be released in May and November, respectively. This change in methodology will reduce the time lag associated with the health insurance index by six months.

Information is available on the medical care factsheet. A more detailed explanation of these changes is available in Improvements to the CPI Health Insurance Index.

Changes to new vehicles methodology (posted March 8, 2023)

With the release of February 2023 data in March, the CPI for new vehicles will modify model changeover processing so that model year changeovers designated as ‘non-comparable’ will be excluded from the year-over-year calculation.

Changes to new vehicles methodology (posted January 4, 2023)

With the release of January 2023 in February, the CPI for new vehicles will introduce a methodology improvement to the time series filter that estimates the most recent cyclical trend and short-term fluctuations. The new vehicles factsheet will also be updated at that time.

Owner’s Equivalent Rent (OER) Unit Weight Refinement (posted September 2, 2022)

Beginning with January 2023 data, BLS plans to adjust the weighting method for Owner’s Equivalent Rent (OER) in the CPI. The new method will use neighborhood level information on housing structure types to weight OER’s unit sample observations.  BLS will continue to sample and weight housing units to be geographically representative.  In some neighborhoods, detached houses are underrepresented in survey responses so additional unit weight will be given to underrepresented detached houses in the OER index sample.  For more information on adjusting housing weights for structure types, see the research article “Location, Location, Structure Type: Rent Divergence within Neighborhoods.”

Last Modified Date: February 13, 2024