Core Inflation Rate YoY

Core Inflation Rate YoY is the 12-month change in All Items Less Food and Energy, a special Consumer Price Index (CPI) aggregate. It covers price change for all urban consumers, over 90% of the US population across 75 urban areas. It has been published since January 1978, and the core series reaches back to January 1957. It excludes rural populations, investment assets such as stocks and houses, producer prices, and differences in price levels between cities. Arabic media call it core inflation in the United States or the core consumer price index. The index uses 1982 to 1984 as 100, so later values show growth since that base period.

Prices are collected through every business day of the reference month, and each figure refers to a full month. BLS releases results monthly under embargo at 8:30 AM Eastern Time, usually 2 or 3 weeks after the month. Each release includes Tables 1, 2 and A plus weights, the database and average prices for the President, Congress and the Federal Reserve. The 12-month rate uses unadjusted data and stays final, while adjusted monthly data are revised each February for the previous 5 years.

Weights (relative importance shares) below are an August 2022 example, since BLS updates them yearly.

• Shelter, 32.470%: rent, owners' equivalent rent (estimated cost of owning) and lodging.
• Services less energy services, 56.833%: shelter, medical care, transport and education services.
• Commodities less food and energy commodities, 21.288%: physical goods excluding food and fuel.
• New vehicles, 4.049%: factory-new car and truck prices.
• Used cars and trucks, 4.008%: volatile second-hand vehicle prices.
• Medical care services, 6.864%: doctor, hospital and prescription-drug services.

In September 2022 core rose 0.6% on the month and 6.6% over 12 months, its largest yearly gain since August 1982. Headline inflation (all items) rose only 8.2% over the same year, down from 8.3%, as gasoline fell 4.9%, showing why core excludes fuel. Shelter rose 0.7% on the month, with rent and owners' equivalent rent each up 0.8%, the largest monthly rise since June 1990.

Shelter rose 6.6% over the year, driving over 40% of the core yearly rise, while medical care rose 1.0% and new vehicles rose 0.7%. Used cars and trucks fell 1.1% and apparel fell 0.3%, offsetting part of the rise.

1. Collect prices: BLS gathers out-of-pocket prices (including sales taxes) through the month across 32 areas and 243 items, or 7776 item-area cells.
2. Basic indexes: Most items use a weighted geometric mean (average of price ratios). Selected shelter, utility and medical services use a Laspeyres formula (ratio of weighted averages).
3. Upper-level aggregation: Higher levels use a modified Laspeyres index (weighted basket) with weights from the Consumer Expenditure Survey (household spending survey). Weights update each January and the index assumes no substitution between items.
4. Reference base: Most series equal 100 in 1982 to 1984, so later values show growth since then.
5. Core subset: Core applies the same machinery to All Items Less Food and Energy only.
6. Reported changes: The 12-month rate uses unadjusted indexes; the 1-month rate uses adjusted indexes from X-13ARIMA-SEATS (seasonal software). Percent change equals (new minus old) divided by old times 100; 279.884 in September 2021 to 298.442 in September 2022 gives 6.6%.