A “like-for-like” lesson from retailers
The habit of product brands to extend by launching new products makes it hard to compare sales from year to year. The brand might be up, say, 5%. But often this is all down to new product launches, and the core product has actually declined. Over time the core product is getting smaller and smaller. And the average sales per product is going down.
For some reason retail brands don’t get away so easily. The industry norm is to report "like-for-like" sales. These results show the sales achieved from existing retail space, stripping out the effect of opening new stores.
This would be a good discipline to use in consumer goods brands. They should report growth based on the same number of products so they can no longer cover up core product decline with brand extension.