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Main points of the 2020-base revision
We will begin to release the 2020-base CPI in August 2021. The 2015-base CPI will also be calculated and released until December 2021. Main points of the 2020-base revision are as follows.
(1) Revision of the CPI reference period
The index reference period of the CPI are revised from 2015 to 2020. We release the 2020-base index from January 2020 retroactively, and the indices before December 2019 are converted into the 2020-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 2020-base CPI are calculated on the basis of average household expenditures by item per month in 2019 and 2020, principally derived from the Family Income and Expenditure Survey (concerned with two-or-more-person households).
Under normal conditions, the weights for CPI are calculated on the basis of average household expenditures in the same year as the CPI reference period, but considering the influence of COVID-19, they are calculated on the basis of two-year average household expenditure for the 2020-base CPI.
(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 2020-base index is 582 (Added items: 30 items; Removed items: 28 items; Integrated items: 10 into 5 items).
(4) Expand adoption of Internet selling prices
Based on the increase in online purchases and the progress in information gathering technology in recent years, we use web scraping technology for making indices of “Airplane fares”, “Charges for package tours to overseas” and “Hotel charges”. And we also use POS (point of sale) information, including both prices in physical and online outlets, for those of “TV sets”, “Video recorders” and “PC printers”, in addition to “Personal computers (desktop)”, “Personal computers (notes)”, “Tablet computers” 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 "Airplane fares", "Electricity" and "Mobile telephone charges" 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) Revision of publishing series and classification items
To enable international comparisons, we release the annual index by COICOP2018. In addition, we continuously release the "Consumption Tax Adjusted CPI" which are the reference results excluding the direct impact of the revision of the consumption tax rate, and also release analysis results about quality adjustment of “Rent”, considering the aging deterioration of the building.
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