However the metric – which is still widely used today – has morphed out of all recognition and can be used in so many ways that it is often meaningless.
Yesterday, Marks & Spencer reported two sets of like-for-likes; one excluding the first day of its post-Christmas sale and one including it.
Next, the rival fashion retailer, is one of a number of retailers to report like-for-likes including online sales and then like-for-likes excluding them. Next says it does this because M&S does. Next also used to report a like-for-like figure for stores "unaffected by new openings", the rationale being that stores affected by new openings would experience "cannibalisation" of sales.
And then there is VAT. Supermarkets report like-for-likes with and without VAT, and occasionally with and without petrol.
The glorious (for retailers) or troublesome (for commentators) thing about like-for-likes is that no definition is wrong. It is not an official measure so can be used in many ways.
Like-for-likes also fail to take all-important profit margins into account.
The first US use of "like-for-likes" appears to have been in the Financial Times in a 1984 piece about Habitat Mothercare, the retail group that was later renamed Storehouse.
Storehouse went kaput years ago. Sadly like-for-likes live on.
