FOI-2023-1237
You asked
May I please request the information on methodology of prices collection for grocery (i.e. Food, Chemist Goods..) in the supermarkets? In the recent years, Clubcard promotions become more popular. Cheaper prices for specific items are available for Clubcard members. I wonder whether the ONS inflation data will capture this behaviour.
We said
Thank you for your request.
Our current approach is to collect the shelf price and not to take account of the discounted price for loyalty card members as our basic collection practice is to only consider discounts if they are available to all. Further information on this approach can be found in section 9.2 of our Consumer Prices Indices Technical Manual.
With that being said, at the end of 2022 we started collecting loyalty card prices alongside the prices used for live production of our consumer price statistics. We recently used this data to conduct an informal (internal) analysis to judge the effect loyalty card discounts would have on our inflation measures if they were included. This exercise did not produce evidence that a hypothetical index created by using the discount prices would be materially different to published CPI at the headline or divisional level.
In early 2025 we plan to incorporate transaction ("scanner") data, obtained from retailers, in our consumer price inflation measures. This data will allow us to calculate the average prices actually paid by consumers, including loyalty card and multibuy discounts, assuming that information is available to us from a given retailer.