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2020-Base Explanation of the Consumer Price Index
PrefaceThe calculation of the Consumer Price Index (CPI) started in August 1946 in Japan. After several revisions, the Statistics Bureau, the Ministry of Internal Affairs and Communications revised the base period and the weight reference period to the calendar year 2020 in August 2021, which is the sixteenth revision.
This manual explains the method of index calculation and main points of the 2020-base revision of the CPI in detail.
January 2022
Statistics Bureau, Ministry of Internal Affairs and Communications
Contents
I Outline of the 2020-Base Consumer Price Index (PDF:170KB)
1 Characteristics of the index
2 Outline of the index
3 Index grouping
4 Publication of the CPI
[Reference] Treatment of the housing services of owner-occupied houses
II Outline of the 2020-Base Revision of the Consumer Price Index (PDF:206KB)
1 Purpose of revision and statistical standard
2 Revision of the index base period
3 Revision of weights
4 Revision of items
5 Expanded adoption of sales prices on the Internet
6 Revision of model formulas
7 Increases and refinement of published groupings
8 Routine review of indices after the base revision, etc.
(Appendix 1) Items added, removed, and integrated in the 2020-base revision
(Appendix 2) Items with name/survey period changed in the 2020-base revision
III Calculation of the Consumer Price Index
Chapter 1 Calculation of the prices in the comparison period (Pt) (PDF:147KB)
1 Calculation of the prices in the comparison period
2 Carry-forward process for seasonal items, less fresh food in non-surveyed months
3 Substitution of the prices in the comparison period
Chapter 2 Quality adjustment during calculation of the prices in the comparison period (PDF:167KB)
1 Necessity of quality adjustment for calculating prices in the comparison period
2 Method of quality adjustment
Chapter 3 Calculation of the prices in the base period (P0) (PDF:132KB)
Chapter 4 Calculation of the weight (W0) (PDF:257KB)
1 Scope of the Family Income and Expenditure Survey (FIES) items adopted for the weights
2 Calculation of the weights for the basic classification indices
3 Calculation of the weights for the goods and services group indices
4 Calculation of the weights for index based on baskets of specific household groups
Chapter 5 Method of index calculation and the index grouping (PDF:225KB)
1 Index formula
2 Process of the index calculation
3 Processing of items for which prices in the comparison period are missing
4 Calculation of average indices for calendar year, fiscal year and so on
5 Calculation of the rate of change
6 Calculation of contribution
7 Index grouping
Chapter 6 Linking of old and new indices (PDF:250KB)
1 Method of linking old and new indices
2 Range of linked indices
3 Notes on the use of linked indices
Chapter 7 Seasonal adjustment (PDF:121KB)
1 Seasonal variation and seasonal adjustment
2 Calculation of seasonally adjusted indices
3 Data used to calculate seasonally adjusted indices
4 Recalculation of seasonally adjusted indices
5 Available grouping of seasonally adjusted indices
[Reference] Method of seasonal adjustment
Appendix 1 Calculation of model items
List of subject items (74 items) (PDF:98KB)
Calculation of model items (Japanese page)
Appendix 2 Calculation of price indices of items using POS information (PDF:252KB)
Appendix 3 Calculation of price indices of items by web scraping (PDF:176KB)
Appendix 4 Calculation of the weights for imputed rent (PDF:310KB)
Appendix 5 Calculation of the CPI by Laspeyres' Chain Index method (PDF:218KB)
Appendix 6 Details of seasonal adjustment with X-12-ARIMA (PDF:84KB)
- ARIMA model setting and prior adjustment of outliers (PDF:157KB)
- Updated (The ARIMA models are applied from the release of Japan December 2021 results, Ku-area of Tokyo December 2021(final) results) (PDF:158KB)
- Updated (The ARIMA models are applied from the release of Japan December 2022 results, Ku-area of Tokyo December 2022(final) results) (PDF:95KB)
- Updated (The ARIMA models are applied from the release of Japan December 2023 results, Ku-area of Tokyo December 2023(final) results) (PDF:91KB)
- Updated (The ARIMA models are applied from the release of Japan December 2024 results, Ku-area of Tokyo December 2024(final) results) (PDF:92KB)
- Updated (The ARIMA models are applied from the release of Japan December 2025 results, Ku-area of Tokyo December 2025(final) results) (PDF:96KB)
IV Related documents for the 2020-Base Consumer Price Index (in Japanese only except for 1)
1 List of information for items of the 2020-Base CPI (PDF:761KB) (Excel:152KB)
2 List of municipalities for the price survey (PDF:421KB) (Excel:26KB)
3 Aggregation table from the items to the groups (basic classification) (PDF:478KB)
4 Aggregation table from the items to the groups (goods and services groups) (PDF:428KB)
5 Aggregation table from the items to the groups (COICOP classification) (PDF:426KB)
6 Division and integration of the FIES items to the CPI items (PDF:1,273KB)
7 Table of correspondence of groups and items in 2020-base and 2015-base (PDF:591KB)
V Weights of the 2020-Base Consumer Price Index (in Japanese only)
1 The number of items and weights by subgroups (Japan / the Ku-area of Tokyo)
(PDF:1,484KB) (Excel:165KB)
2 The number of items and weights by goods and services groups (Japan / the Ku-area of Tokyo)
(PDF:398KB) (Excel:18KB)
3 Weights by subgroups (City groups / District / Cities with Prefectural Governments)
(PDF:820KB) (Excel:85KB)
4 Monthly weights of fresh food (Japan / the Ku-area of Tokyo)
(PDF:591KB) (Excel:36KB)
5 Weights by specific household groups (Japan)
(PDF:482KB) (Excel:39KB)
6 Weights by goods groups classified according to elasticity to living expenditure (Japan)
(PDF:605KB) (Excel:59KB)
7 Weights by annual purchase frequency classes (Japan)
(PDF:577KB) (Excel:75KB)
8 The number of items and weights by COICOP classification (Japan)
(PDF:401KB) (Excel:22KB)
VI History of the CPI in Japan (PDF:69KB)
VII Outline of the Retail Price Survey (Trend Survey) (PDF:113KB)
1 Purpose
2 Survey system and survey areas
3 Survey items and specifications
4 Survey date
5 Survey methods
6 Number of collected prices
VIII Reference materials (in Japanese only) (PDF:433KB)
1 Resolution concerning consumer price indices, adopted by the 17th International Conference of Labour Statisticians (2003) -excerpt-
2 Application examples of the Consumer Price Index
3 Japanese statistical standard on the base period of index
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