Tokyo Core CPI YoY

Tokyo Core CPI YoY is the year-on-year change, versus the same month last year, in the Ku-area consumer price gauge less fresh food. Core means All items, the full basket, less fresh food of fish, vegetables and fruits.

Japan's Statistics Bureau publishes it monthly from the Retail Price Survey, a monthly shop-price survey. It covers 582 items in 167 municipalities, with some prices from scanner data and web scraping. It covers household goods and services and weights items by household spending.

It counts owner housing by imputed rent, equivalent rent, and excludes direct taxes and land and housing purchases. Calculation started in August 1946 and has used retail prices since 1952.

Prices are surveyed on Wednesday, Thursday or Friday of the week including the 12th, with 40 perishable items checked 3 times monthly.

The Tokyo Ku-area-only flash, a preliminary, leads national results and appears at 8:30 AM Japan time Friday of the week including the 26th, in principle. National figures for the previous month appear at 8:30 AM Japan time on Friday of the week including the 19th, in principle. Each release shows 3 headline series with index, a level versus the base year set to 100, yearly change and seasonally adjusted monthly change.

The base is revised every 5 years with no recalculation of published change rates. Tables also appear on e-Stat.

10 major household groups move it, and core keeps energy while dropping fresh food.

• Food: everyday food except fresh fish, vegetables and fruits.
• Housing: rent paid by tenants plus owner housing counted as equivalent rent.
• Fuel, light and water charges: It covers electricity, gas and water for homes. Energy's 5 items of electricity, piped gas, propane, kerosene and gasoline stay in core.
• Transportation and communication: fares and phone charges including airplane fares and mobile-phone charges.
• Culture, recreation and education: leisure and school fees such as theme-park visits and overseas package tours.
• Furniture, clothes, medical care and miscellaneous: household goods, clothing and footwear, medical care and other items.

The December 2023 flash, released 9 January 2024, shows the core-energy split. All items stood at 106.5, up 2.4% yearly, while core stood at 106.1, up 2.1% yearly.

Core-core, or less fresh food and energy, stood at 105.8, up 3.5% yearly, a full point hotter than All items, showing energy pulled it down. The table also shows cooling: November was 2.7% for All items, 2.3% for core and 3.6% for core-core, while October was 3.2%, 2.7% and 3.8%. Seasonally adjusted monthly change was 0.0% for All items and 0.2% for core and core-core.

1. Fixed basket: The index uses a fixed base-year basket under the Laspeyres formula, so it compares current prices for the same goods with base-year prices.
2. Item index: Each item index divides current price by base-year price and multiplies by 100, after quality adjustments and seasonal carry-forward for off-season clothing. Electricity and mobile-phone charges use model formulas.
3. Averaging: Municipality item indices are averaged with municipality weights, then items are averaged with spending weights level by level. Missing prices are excluded and filled by the remaining group index, while fresh-food items use monthly weights.
4. Yearly rate: Yearly change divides the index minus its year-ago level by the year-ago level and multiplies by 100, using unrounded indices. Tables round yearly change to 1 decimal place.
5. Contribution: Contributions measure each item's share of total change. In the illustration, rice contributes 1.40 points.
6. Core extraction: Core is found by removing fresh food with residual math.
7. Worked illustration: A simple illustration uses rice at weight 7000 and electricity at weight 3000. If rice is 102.0 and electricity is 98.0, All items is 100.8, and versus 99.0 last year the yearly rate is 1.8%.
8. Seasonal adjustment: Seasonal adjustment covers 5 series for Japan and the Ku-area, uses X-13ARIMA-SEATS, and yearly comparison also removes seasonality.