Japan: Estimating impact of 2025 CPI rebasing

Research evidence excerpt

Japan: Estimating impact of 2025 CPI rebasing

Global Markets Research

Japan: Estimating impact of 2025 CPI rebasing 13 July 2026

Economics - Japan

We estimate: (1) broadly unchanged core and core-core CPI Research Analysts

figures; (2) small upward revisions for inflation ex food Japan Economics

Uichiro Nozaki - NSC

Some uncertainty will remain until retroactive revisions are announced uichiro.nozaki@nomura.com

+81 3 6703 1284

Kyohei Morita - NSC • The Ministry of Internal Affairs and Communications (MIC) has released the details of

kyohei.morita@nomura.com

the 2025 consumer price index (CPI) rebasing. Retroactively revised inflation rates for +81 3 6703 1395

Jan–Jun 2026 using the new base will be announced on 7 August.

• We estimate that core and core-core CPI inflation figures will remain largely

unchanged even after these revisions. Our estimates suggest, however, that there wil

be small upward revisions to inflation figures excluding food (close to the definition of

core CPI used in the US).

• Our calculations do not factor in the addition of new items or changes in calculation

methods for some existing items. Some uncertainty will therefore remain until the

retroactive revisions are announced.

2025 CPI rebasing: Details of revision plan released

On 10 July, MIC published details on the upcoming rebasing of the CPI to 2025. The

outline of the rebasing plan itself was released in November 2025 (see our 20 January

2026 report Japan:Keypointstowatchin2025CPIrebasing). The new rules include: (1)

the weighting of individual items and categories under the new base; and (2) the details of

the calculation methodologies for "model items" (items for which indices require special

computation because of their diverse pricing structures).