South Africa, Jan. 28 -- It's 2006 and John delivers a victorious share story to the board. As a first-time CMO, he takes excess pride in the persistent market share increase of their mobile phone brand. The only problem is that the category itself is decreasing. Months later, smartphone usage exploded, and their own business collapsed. Nokia, Blackberry, and even Kodak fit the description: they were growing in a declining category.

Yorkshire Tea knows this first-hand, as the volume sales for ordinary tea have been on a steep decline over the last three years. Despite their own successive annual share gains, they needed to find new space and remain on the lookout for stretching opportunities, for their own brand, and the broader category...