How Brands Grow by Byron Sharp: A Research Review

Work reviewed. Sharp, B. (2010). How Brands Grow: What Marketers Don't Know. Oxford University Press, New York. Extension: Romaniuk, J. & Sharp, B. (2016). How Brands Grow: Part 2. Oxford University Press. Research base: the Ehrenberg-Bass Institute for Marketing Science, University of South Australia — continuous consumer-panel data across categories and countries.

TL;DR. How Brands Grow is the book that turned half a century of marketing orthodoxy on its head. Byron Sharp's central claim is brutally simple: brands grow by getting more buyers — however light and disloyal — not by deepening loyalty among the ones they already have. The mechanics are penetration, mental availability, distinctive assets, and the lawful patterns of double jeopardy. It matters because almost every default marketing instinct — reward your loyalists, differentiate to stand out, target your heavy users — is, in Sharp's evidence, pointing the wrong way.

If The Long and the Short of It is the modern marketer's budget manual, How Brands Grow is the physics textbook. Where Binet and Field tell you how to split the money, Sharp tells you what the money is actually buying: memory structures, availability, and incremental buyers. This review covers the laws Sharp proposes, the most useful — and most uncomfortable — implications, and where the work legitimately gets challenged.

What is 'How Brands Grow'?

How Brands Grow (2010) is the popular-facing synthesis of decades of empirical work by the Ehrenberg-Bass Institute, the marketing-science research centre at the University of South Australia, led by Byron Sharp. Its subtitle — What Marketers Don't Know — sets the tone: this is a deliberately polemical book, written to demolish comfortable beliefs with panel data.

The evidence is not a survey of opinions. It is continuous consumer-panel purchase records — the kind that track what thousands of households actually buy, week after week, across categories from baked beans to banking and across many countries. From that data, Ehrenberg-Bass and its forebears (notably Andrew Ehrenberg himself) built a set of empirical generalisations about how brands compete. The headline is that brand competition is strikingly lawful and predictable, and those laws leave very little room for the loyalty-and-differentiation story most marketing was built on.

The book distils this into seven rules for growth, each backed by the same panel-data logic. Before listing them it helps to understand the two laws underneath.

What are Sharp's seven rules — and the laws behind them?

Underneath the seven rules sit two empirical regularities that do most of the explanatory work.

The Law of Double Jeopardy. Smaller brands suffer twice: they have fewer buyers, and those buyers buy them slightly less often. A small-share brand's lower loyalty is not a failure of its CRM programme — it is a mathematical consequence of being small. Big brands look "more loyal" mainly because they are bigger. This pattern, originally described by William McPhee and adapted to markets by Ehrenberg, holds across categories and countries with eerie consistency.

The Dirichlet. A statistical model (the NBD-Dirichlet) that describes — and predicts — the market shares, penetration, and purchase frequencies of competing brands in a stable category. When brands roughly obey the Dirichlet, it tells you the category is behaving like a normal competitive market. It is the formal backbone of the whole framework.

Against that backdrop, Sharp's seven rules for growth are, paraphrased faithfully:

Continuously reach all buyers of the category — through communication and distribution. Don't chase a narrow band of heavy loyalists; most of a brand's sales come from light and occasional buyers.
Ensure the brand is easy to buy — physical availability, distribution, shelf and digital presence.
Get noticed — at the moment of purchase, distinctiveness beats subtle persuasion.
Refresh and build memory structures — link the brand to the category entry points that cue buying.
Create and use distinctive brand assets — logos, colours, typefaces, taglines, characters — so the brand is instantly recognisable.
Be consistent, yet fresh and contemporary — keep the assets stable over time so memory compounds.
Stay competitive — don't give buyers a reason to defect. Don't irritate customers; the job is to remain in the consideration set, not to engineer unbreakable devotion.

Notice what is not on the list: differentiate meaningfully, target your heaviest buyers, build loyalty, nurture the loyalty ladder. That omission is the point, and it is the source of most of the book's controversy.

Penetration vs loyalty — which one actually grows brands?

If the book has one message a marketer must internalise, it is this: growth is a penetration game, not a loyalty game.

Across the panel data, the difference between a big brand and a small one is almost entirely how many people buy it, not how devotedly. Big brands have marginally higher repeat-purchase rates and share-of-category requirements — but those loyalty metrics move far less than market share does, and they are largely predicted by a brand's size. In other words, loyalty metrics look like outputs of penetration, not independent levers.

This overturns the "80/20" instinct — the idea that a brand's profits flow from a devoted core of heavy buyers whom you should cherish and upsell. Sharp's data shows the heavy-buyer core is smaller and more replaceable than the doctrine suggests, and that the bulk of any brand's volume comes from the light and occasional buyers who drift in and out. The strategic implication: compete for the whole category, including the people who barely buy you and the people who don't buy you yet. A loyalty programme that merely defends existing frequency is unlikely to move the growth needle; reaching more buyers is what does.

It is worth being precise about the claim. Sharp is not saying loyalty is worthless — retention matters, and defection is expensive. He is saying that loyalty differences between competing brands are too small and too share-driven to be the engine of growth. The engine is penetration. That is a narrower, more defensible claim than "loyalty is dead," but it is still heresy to a marketing culture organised around CRM, segmentation by value, and the loyalty ladder.

How do brands get bought — mental availability and distinctive assets?

If penetration is the goal, how do you get more buyers? Sharp's answer runs through two connected concepts that the sequel, How Brands Grow 2 (Romaniuk & Sharp, 2016), develops in depth.

Mental availability is the probability that a buyer thinks of your brand in a buying situation. It is emphatically not "awareness" — a respondent can be aware of a brand and never think of it when it matters. Mental availability is built by linking the brand to the many situations, needs, and triggers that lead to a purchase — what Romaniuk calls category entry points. A brand that owns more entry points (more buying occasions it gets cued for) gets thought of more often, and gets bought more often, almost by definition.

Distinctive assets are the non-name elements that identify a brand without it being spelled out — a colour, a shape, a character, a sound, a font, a line. Their job is not to "differentiate" in the sense of conveying a unique benefit; it is to make the brand unmistakably itself, so that every exposure reinforces the memory structure rather than leaking into generic category memory. The rule is to build them, register them, use them consistently, and protect them — because they are the filing system by which mental availability compounds.

This reframes "creativity" and "consistency" in hard, measurable terms. The question is not "is our advertising on-brand?" in some vibes-y sense. It is "are we consistently depositing more cues against more category entry points, using assets the market reliably recognises?" That is a question you can actually track — and it is why the Ehrenberg-Bass work pairs so naturally with the Binet and Field emphasis on long-term brand building. Both traditions say the same thing about what brand spend is for: building memory and availability so you get bought more often.

What does Sharp get challenged on?

How Brands Grow is revered and resented in roughly equal measure. A research review owes you the serious critiques, not just the applause. Four recur:

1. "Differentiation doesn't matter" overstates the finding. This is the most-contested claim. Sharp shows that perceived differentiation between competing brands is, in survey data, surprisingly small, and argues distinctiveness (being recognised) matters more than differentiation (being seen as uniquely better). Critics argue this conflates survey-measured similarity with genuinely meaningful positioning, and that it straw-mans differentiation into a cartoon. The more defensible Ehrenberg-Bass position is "competing brands are largely substitutable, so bet on distinctiveness and availability" — but the book's rhetoric often reads as "differentiation is a myth," which goes further than the data strictly license.

2. The Dirichlet fits stable, repeat-purchase, FMCG-style markets best. The model describes packaged-goods competition beautifully; its fit weakens for high-involvement or considered purchases, premium and luxury, services and subscriptions, B2B, and fast-moving or new categories. Generalising "growth is all penetration" to a subscription business with high switching costs, or a considered B2B purchase, requires care. Loyalty and retention economics can be genuinely central in those settings.

3. "Loyalty is a myth" is a misreading the book sometimes invites. The defensible claim is that between-brand loyalty differences are small and share-driven. That is not the same as "retention doesn't matter." In high-margin, relationship-driven, or 95:5 rule B2B contexts, keeping the customers you have can be the dominant lever. Critics say the polemical framing has led marketers to under-invest in retention where it genuinely pays.

4. The "stop targeting heavy buyers" implication is overstated. Sharp's point is that you cannot grow by only marketing to your loyalists — the light and non-buyers hold the growth. That is well-supported. But some readers have taken it as "heavy buyers don't matter," which is neither what the data shows nor what Sharp ultimately claims. The target is a dogma, not the practice of value-based segmentation itself.

None of this sinks the book. It does mean How Brands Grow is best read as a set of powerful empirical generalisations with a clear domain — competitive, repeat-purchase markets — rather than a universal law of all commerce. Read it that way and it is unimprovable. Read it as gospel for every category and you will over-rotate.

How do you apply it?

The book's value is operational, not philosophical. Here is how to put the laws to work:

Set penetration as the primary growth metric. Track the number and reach of your buyers — including the light and lapsed — ahead of loyalty indices. Growth that isn't showing up in penetration probably isn't growth.
Market to the whole category, not just your heavy users. Budget for broad reach and for the non-buyers you don't yet have. Rewarding only your heaviest buyers is a defensive posture dressed up as strategy.
Build and protect distinctive assets. Inventory the cues that identify your brand, use them relentlessly and consistently, and resist the urge to "refresh" them into unrecognisability every campaign.
Expand your category entry points. Map the situations and needs that cue purchase in your category, and ensure your brand is linked to more of them — that is what compounds mental availability.
Invest in physical availability. Distribution, shelf, search, and ease of purchase are not the unsexy part of marketing; in Sharp's world they are half the job.
Calibrate the loyalty verdict to your category. In mass repeat-purchase markets, treat loyalty as an output. In subscription, high-margin, or considered B2B contexts, keep retention central — the laws bend, even if they don't break.

Key takeaways

How Brands Grow (Sharp, 2010) argues that growth comes from penetration — more buyers, however light — not from deepening loyalty, and backs it with decades of consumer-panel data.
Two laws do the work: double jeopardy (small brands lose on both buyer numbers and frequency) and the Dirichlet (brand competition is strikingly predictable).
The engine is mental availability (being thought of in buying situations) plus distinctive assets and physical availability — not meaningful differentiation.
Sharp's seven rules collapse to: reach the whole category, be easy to buy, be noticed, build memory, and don't give buyers a reason to leave.
It gets legitimately challenged on overstating the "differentiation is dead" and "loyalty is a myth" claims, and on how far the Dirichlet generalises beyond stable, repeat-purchase, FMCG-style markets.

Market Penetration — the growth metric Sharp centres
The Double Jeopardy Law — the empirical regularity under the framework
Mental Availability — the mechanism of being thought of
Distinctive Assets — the memory structures that drive recognition
Category Entry Points — the buying cues that compound availability

About the author

Byron Sharp is Professor of Marketing Science and director of the Ehrenberg-Bass Institute for Marketing Science at the University of South Australia, whose continuous consumer-panel research across categories and countries underpins the book. How Brands Grow (Oxford University Press, 2010) set out the empirical laws — penetration, double jeopardy, the limits of loyalty — summarised in this review. The follow-up, How Brands Grow: Part 2 (with Jenni Romaniuk, Oxford University Press, 2016), extends the framework to mental availability, category entry points and market assets.