I’d be astonished if it doesn’t. The government itself might be duplicitous as anything, and the population might at times be too stupid to notice, but I would normally assume the ONS is neither of those things for the most part.
I did look at an ONS report into this published in 2019, and it looks like they do consider some "standard" items but not all.
www.ons.gov.uk/economy/inflationandpriceindices
6.Estimating the proportion of products in the CPIH basket with size changes
Our sample is fixed throughout the year; price collectors attempt to track the price of a particular item in the sample from month to month. We have estimated the proportion of all food and drink items we tracked in 2016 that changed size1 (note that the items tracked are not all distinct products, as the same item may be tracked in different outlets and locations).
When calculating this figure, we considered the fact that not all food and drink quotes had the potential for a size change to be identified, as we do not record size as a quality indicator for all quotes2. In total, around 46% of food and drink quotes had a size recorded in 2016.
Many of those quotes without sizes recorded are unlikely to have a size change as they are a standard-sized product (such as a 250 gram block of butter) and others do not typically have a set size (for example, whole fruits and vegetables). However, for some items such as cheese, it is possible for products to change size, but we work on a basis of price per unit weight, so we do not need to record absolute sizes for our quality adjustment processes.
We have therefore calculated upper and lower bounds for the proportion of all food and drink items we tracked in 2016 that changed size, with the upper bound taking the number of size changes over the number of quotes with a size recorded and the lower bound taking the number of size changes over the total number of quotes, including those without a size recorded. The upper bound is likely to be an overestimation, as the items excluded from the calculation are disproportionately those that are less likely to have size changes, while the lower bound is likely to be an underestimation, as there are likely to be some products that changed size that were not identified.
Throughout 2016, our monthly sample contained an average of 37,408 food and drink items, of which on average around 17,100 had a weight recorded. Across 2016, we identified 361 tracked items with a size reduction and 116 with a size increase. Therefore, we estimate that between 1.0% and 2.1% of tracked items had a size decrease and between 0.3% and 0.7% of tracked items had a size increase.
Further methodological details and limitations are described in Annex A.
Notes for: Estimating the proportion of products in the CPIH basket with size changes
- Food and drink items within COICOP class 1 (Food and Non-Alcoholic Beverages) and 2 (Alcoholic Beverages and Tobacco) were included while those within COICOP class 11 (Restaurants and Cafes) were not included.
- There are several reasons why quotes may not have a size recorded:
- the weight or volume may be fixed at a standard size (for example, “Large loaf white unsliced 800 grams”)
- the quantity may always be a single unit of goods (for example, “Doughnut, each”)
- the price may be calculated per unit weight (for example, “Bacon, back, per kilogram”)
- the size of the product may not be applicable when describing the product’s quality (more relevant to non-food items)
- a size measurement may not be available for the particular product whose price is quoted
In cases where the exact weight or volume of an item is specified, a size change that took a product’s size outside of this range would normally trigger its replacement with a different product of the specified size. Alternatively, a size change could result in a change to the item description to ensure that we can continue to collect a particular product or product range that has changed in size.
