Inflation Rate YoY

Inflation Rate YoY is the 12-month percentage change in United Kingdom consumer prices, not the index level itself. It comes from two indices compiled by the Office for National Statistics (ONS). CPIH is the lead comprehensive index including owner occupiers housing costs (OOH), while CPI is the harmonised counterpart excluding OOH.

Coverage spans private households, foreign visitors and communal residents across the economic territory of the United Kingdom. The basket holds about 700 items priced across 141 locations with over 100000 price quotes each month. It tracks average change in a fixed basket, not the cost of living, so any single household differs from the average.

Prices reflect at least 1 working week near mid-month on the same day each month. Motor fuel prices average across the month from weekly prices, and fresh produce has a second collection day. The bulletin appears at 7am in the middle of the month following the reference month, with schedule announced in advance on the release calendar.

Each issue publishes headline indices with 12-month and 1-month rates, core measures excluding energy, food, alcohol and tobacco, goods and services splits, contributions and weights. There is no pre-release access except use by the Bank of England policy committee, and method changes do not revise published rates. Errors above 0.1 percentage points on a headline annual rate carry a public correction notice. Markets read the rate against a 2% target, and a move above 3% or below 1% triggers a letter from the Governor to the Chancellor.

Moves track broad household spending divisions, each weighted by its share of expenditure and scaled by its own 12-month price change. Division weights sum to 1000 parts, so each contribution is about weight multiplied by its price change.

Housing, water, electricity, gas and other fuels, 301.205 of 1000: energy bills, rents and, in the comprehensive index only, owner housing costs.

Owner occupiers housing costs, 170.735 of 1000: imputed rents owners would pay, present in the comprehensive index and absent from the harmonised index.

Recreation and culture, 119.177 of 1000: leisure goods, entertainment and package holidays.

Restaurants and hotels, 109.535 of 1000: catering and accommodation prices.

Transport, 106.000 of 1000: motor fuels, vehicles and fares, often the largest mover of the headline rate.

Food and non-alcoholic beverages, 90.194 of 1000: everyday grocery prices.

For example, the harmonised rate reached 11.1% then eased to 10.7%, while the comprehensive rate moved from 9.6% to 9.3%. Prices still rose 0.4% in the easing month, but the annual rate fell because the comparison month had risen 0.7%. Transport gave the largest downward pull while rising catering prices partly offset it.

The harmonised rate ran about 1.4 points above the comprehensive rate as energy surged while owner housing rose about 3.6%.

1. Elementary aggregates: where no spending weights exist, quotes combine by unweighted formula, mainly the Jevons index, the geometric mean of price relatives.

Dutot, the ratio of average prices, serves some items, while Carli, the arithmetic mean of relatives, is banned for causing chain drift.

1. Item indices: cells split by shop type and region combine using shop weights into each item index.

1. Lowe aggregation, fixed-basket averaging: classes, groups, divisions and the all-items index form weighted arithmetic means using annual spending weights.

Weights refresh each year and the item basket refreshes separately.

1. Chain-linking: yearly weight and basket changes relink the index.

The chain maps onto a fixed reference where the base equals 100 units.

1. 12-month rate: the annual rate divides the unrounded index change by the earlier index and multiplies by 100 to obtain the rate.

For example, 130.0 rising to 133.9 gives 3.0% to 1 decimal place, and a division weighted 106 of 1000 rising 5.0% adds about 0.53 points.

The rate is no cost-of-living gauge and the two indices differ, since only the comprehensive index carries owner housing. So the 2 rates differ.