Category definitions: whose category is it?

Every share figure depends on a denominator, and the denominator is a category boundary somebody drew. Manufacturers, retailers and data providers draw them differently, and each boundary is defensible from where it was drawn.

A share number without its category definition is not a claim that can be checked.

Why do definitions differ?

Because the parties are answering different questions. A manufacturer defines a category around competitive substitution — what a shopper would buy instead. A retailer defines it around shelf management — what sits together and is bought together. A data provider defines it to be consistent and comparable across the whole market.

None of those is wrong and they produce different denominators and therefore different shares.

What does a wider category do to a share?

Reduces it, obviously, and changes what growth means. A brand can gain share in a narrow definition and lose it in a wide one in the same period if the wider category contains a fast-growing adjacent segment.

That is not manipulation when it is disclosed. It becomes manipulation when the definition is chosen after the result is seen.

How should a brand choose its definition?

From the question. For a competitive strategy discussion, the substitution-based boundary is the meaningful one. For a retailer conversation, the retailer's boundary is the one that matters, because it is the one governing shelf decisions.

Holding both is normal and healthy. Reporting only the flattering one is the failure mode.

What about emerging segments?

They are where definitions age fastest. A format that did not exist three years ago sits outside every established boundary until somebody moves it, and where it sits materially changes several parties' numbers.

That is worth watching deliberately. A category whose definition has not been revisited while the market changed is producing shares about a market that no longer exists.

How does this affect growth reporting?

Category growth is as definition-dependent as share. A category that grew because its boundary widened did not grow, and a report that changed definition between periods without saying so is reporting an artefact.

Any definitional change should be accompanied by a restated history on both bases, at least for the comparison period.

What should appear alongside a share figure?

The category definition, the geography, the channel, the period and the measure. Five clauses. A share quoted without them can be reconciled with almost anything and refuted by nothing.

How do retailer and manufacturer views get reconciled?

By translating rather than arguing. A manufacturer bringing its own boundary to a category review is bringing a number the retailer cannot act on; translating the analysis into the retailer's structure is what makes it usable.

That translation is work and it is what distinguishes a category conversation from a brand pitch.

Does the independent channel complicate this?

Yes, because shelf structures vary store to store and there is no central planogram. A category defined by adjacency in a chain has no equivalent definition in a channel where every operator arranges the shelf their own way.

In that channel, substitution-based definitions travel better than adjacency-based ones. Industry context is collected by trade bodies such as NACS and FMI.