The Core CPI is calculated by comparing the cost of a fixed basket of goods and services in the current year to the cost in the previous year. This basket is carefully constructed to represent the typical consumption patterns of households in the UK, excluding food and energy items.
To determine the cost of the basket, the Office for National Statistics (ONS) collects price data from a wide range of retailers and service providers across the country. This data is then weighted to reflect the relative importance of each item in the basket. For example, items that are frequently purchased or that make up a larger portion of household budgets will have a higher weight in the calculation.
The percentage change between the cost of the basket in the current year and the previous year represents the annual inflation rate. If the cost has increased, it indicates that prices have risen, leading to inflation. Conversely, if the cost has decreased, it indicates that prices have fallen, leading to deflation.
The ONS uses a variety of methods to collect price data, including surveys, field visits, and online data collection. The data is then carefully analyzed and adjusted to account for changes in quality, product substitution, and other factors that can affect prices.
Once the cost of the basket has been determined, the Core CPI is calculated by dividing the current year’s cost by the previous year’s cost and subtracting 1. The result is expressed as a percentage, representing the annual inflation rate.