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Main points of the 2025-base revision
We will begin to release the 2025-base CPI in August 2026. The 2020-base CPI will also be calculated and released until December 2026. Main points of the 2025-base revision are as follows.
(1) Revision of the CPI reference period
The index reference period of the CPI is revised from 2020 to 2025. We release the 2025-base index from January 2025 retroactively, and the indices before December 2024 are converted into the 2025-base and linked to enable time-series analysis. However, the rates of change are not recalculated with the linked index but the published values for every base period are used unmodified.
(2) Weight revision
The weights used for the 2025-base CPI are calculated on the basis of average household expenditures by item per month in 2025, principally derived from the Family Income and Expenditure Survey (concerned with two-or-more-person households).
(3) Revision of items
Items whose importance for household consumption expenditure has increased or decreased are added or removed respectively from the index items. As a result, the number of items used for the 2025-base index is 589 (Added items: 19 items; Removed items: 11 items; Integrated items: 2 into 1 item).
(4) Expanded adoption of Internet selling prices
Based on the increase in online purchases and the progress in information gathering technology in recent years, we expand to use POS (point of sale) information, including both prices in physical and online outlets, for those of "Memory cards" and "Ink cartridges for printer", in addition to "TV sets", "Video recorders", "Personal computers (desktop)", "Personal computers (laptop)", "Tablet computers", "PC printers" and "Cameras", for which we have used it from before.
(5) Revision of the price index calculation method using a model formula
Some items such as "Electricity" and "Telephone charges(moblie phone)" have various fare structures, with prices that vary according to the purchased conditions. To accurately reflect the price fluctuation in the price index, monthly indices for these items are calculated with a special formula (model formula) which is designed by using a typical utilization case of each item as a model. We revise the component ratios of prices and the choices of model cases used in model formulae to accurately reflect actual conditions to the price indices.
(6) Enhancement of Published Series
CPI rounded to three decimal places is available for Japan and is now also available for the Ku-area of Tokyo for users' convenience in replicating the published rate of change.
The format of the COICOP group index is changed from monthly results tables to a time-series table.
(7) Change in the software used for seasonal adjustment
The software used for seasonal adjustment is switched to the latest version, X-13ARIMA-SEATS.
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