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2020-Base Explanation of the Consumer Price Index

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)

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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