How brands grow: the Ehrenberg-Bass laws, and the debate around them

In 2010 Byron Sharp and the researchers of the Ehrenberg-Bass Institute published How Brands Grow with Oxford University Press¹. Its argument, extended in How Brands Grow: Part 2 by Jenni Romaniuk and Sharp², is that buying behaviour follows regular, repeatable patterns, and that marketing plans should start from them.

• Double jeopardy Smaller brands have far fewer buyers, and those buyers buy them a little less often³.
• Duplication of purchase A brand shares its buyers with other brands in line with those brands' size⁵.
• Mental and physical availability Growth comes from being easily thought of in buying situations and easy to buy⁷.
• Category entry points and distinctive assets The cues that bring a category to mind⁷, and the brand's own colours, shapes and sounds that make it recognisable⁸.
• The debate Binet and Field, Mark Ritson and others accept much of this but disagree on targeting, emotion and differentiation^{10, 12, 14}.

The decision it informs: whom the plan should reach, how broadly, and what must stay the same in every execution. Read it with brand equity and the glossary entries for mental availability and category entry points.

Double jeopardy. The pattern was first documented in the 1960s⁴. Andrew Ehrenberg, Gerald Goodhardt and Patrick Barwise reviewed the evidence in the Journal of Marketing in 1990: a small brand typically has far fewer buyers than a large one, and its buyers also tend to buy it less often³. The Ehrenberg-Bass Institute puts it plainly: loyalty is largely a predictable function of market share, brands differ greatly in how many customers they have but much less in how loyal those customers are, and so a brand that wants to grow must enlarge its customer base, its penetration⁴. The Institute's 2021 work with B2B data found the same pattern in business markets⁴.

Duplication of purchase. The second law describes competition. A brand's customers also buy other brands, and they buy each competitor in line with that competitor's size⁵. In one US business-insurance dataset reported by Marketing Week, the share of a brand's customers who also used another insurer fell from about 24% for the largest competitor to about 14% for the smallest⁵. Romaniuk's conclusion for B2B marketers is that your main competitors will typically be the biggest brands in the category, whatever your image or positioning⁶.

Practically, these laws give a planner a baseline. If your brand's loyalty is in line with its share, a loyalty problem is really a penetration problem. If two brands share far more buyers than their sizes predict, you have found a real sub-market, and a reason to treat it differently.

Romaniuk sums up the two levers in a sentence: mental availability is about being easily thought of in buying situations, and physical availability is about being easy to buy⁷.

Mental availability is built in memory. It depends on how many buying situations the brand is linked to and how strongly. That is why the research cares less about whether people like a brand and more about whether it comes to mind at the moment of choice. Brand advertising, sponsorship, PR, packaging and search presence all contribute, provided they leave a memory people can retrieve later.

Physical availability is distribution in the widest sense: being on the shelf, in the app, on the marketplace, open at the right hours, in stock and simple to pay for. It is often outside the marketing department's budget, but it caps what communication can achieve: a brand that people think of and then cannot find loses the sale to the one they can.

Category entry points (CEPs) are the cues buyers use to retrieve memories in a buying situation: internal ones such as motives and emotions, and external ones such as location or time of day⁷. They decide which brands are initially mentally available and so form the shortlist of first options⁷. "Something quick for lunch at my desk" and "a gift for a colleague who is leaving" are CEPs; each brand is linked to some and not to others.

Distinctive assets are what lets a brand be recognised without its name: colours, logos, characters, sounds, taglines. Romaniuk's Building Distinctive Brand Assets sets out how to build, measure and protect them, judging each by its fame and its uniqueness⁸. In an integrated plan they are the glue: they let a ten-second video, a shelf wobbler and a social post be credited to the same brand. See distinctive brand assets.

The laws are widely accepted as descriptions of buying. How far they should dictate marketing is argued.

Targeting. Ehrenberg-Bass research on B2B argues that narrow targeting is counter-productive to growth⁹. Les Binet and Peter Field's Media in Focus for the IPA asked whether mass marketing still works and whether tight targeting is now more efficient¹⁰; Field's own profile summarises their view that high-quality mass campaigns beat laser-focused strategies most of the time¹¹. Mark Ritson, writing in Marketing Week, credits Sharp with shifting the industry towards mass marketing¹² but calls abandoning targeting a return to the dark ages, and argues that broad reach and targeting can coexist¹³.

Emotion. Binet and Field's analysis of IPA cases suggests that the more emotional the purchase decision, the more efficiently advertising media work, while rational categories tend to get more of their growth from factors other than advertising¹⁰.

Differentiation. Here the disagreement is real. Ritson argues for relative differentiation: a brand has more of something its buyers value, even if it is not unique¹². Sharp, by contrast, argues from his research that buyers in most categories notice few of the differences brands try to communicate¹². When he and Sharp shared a stage at Cannes Lions they agreed on salience and mental availability but not on the role of differentiation¹⁴.

Method. Some researchers question the statistics. Hofmeyr and Bongers argue that modelling averages hides important differences between brands, in a critique of double jeopardy published by WARC¹⁵; the Institute replies that the critique targets the Dirichlet model used to predict the pattern rather than the empirical pattern itself¹⁶.

A fair reading: the laws describe the market you are in and set realistic expectations. They do not tell you what to say, and they do not forbid choosing whom to say it to first.

• Reach Plan the media for reach among category buyers, then decide frequency. A plan that only re-targets existing customers works against double jeopardy⁴.
• Consistency Distinctive assets only work if they are used every time⁸; this is where consistency and adaptation becomes a growth issue, not a style issue.
• The media plan Use the media plan to cover the entry points that matter most, and judge budgets against share of market with share of voice and the ESOV calculator. Balance long-term brand building against short-term activation, as in budgeting for IMC.
• B2B and services too The B2B work on double jeopardy, duplication and entry points shows that the patterns are not only for packaged goods^4, 6, 7; see the B2B and SaaS hub.

1. Using the laws as a reason not to think They describe averages across brands; your category may have real partitions, which duplication analysis will show⁵.
2. Confusing distinctive with different A distinctive asset helps people recognise you; it is not a reason to buy, and a brief still needs one.
3. Cutting brand media to fund retargeting It looks efficient on last-click reports and shrinks the future buyer base.
4. Ignoring physical availability Communication cannot sell what people cannot find.
5. Treating the debate as a war The best-documented positions share more than they disagree on¹⁴.

Illustrative example. A mid-sized snack brand is losing share. Its team checks loyalty against share and finds it normal for its size, so the problem is penetration. It lists the category's entry points (a mid-afternoon dip, a long drive, guests arriving), finds the brand linked mainly to one, and briefs a year-long campaign to add the second. Every execution opens with the brand's colour and mascot, and the sales team secures distribution at fuel stations to match.

Your checklist for Monday:

1. Pull penetration and purchase frequency for your brand and its top competitors.
2. Write down the ten most important category entry points, with the buyers' own words.
3. Ask a sample of category buyers which brands come to mind for each.
4. List your distinctive assets and score each for fame and uniqueness.
5. Rebalance the media plan towards reach among category buyers, then check continuity across the year.
6. Agree one physical-availability action with sales or operations.
7. Report mental availability alongside sales, quarterly, to the CMO.

• Byron Sharp, How Brands Grow (Oxford University Press, 2010)¹, and Jenni Romaniuk and Byron Sharp, How Brands Grow: Part 2 (2021)².
• Ehrenberg, Goodhardt and Barwise, "Double Jeopardy Revisited" (1990)³.
• Jenni Romaniuk, Building Distinctive Brand Assets (2018)⁸, and her paper on category entry points in B2B⁷.
• Binet and Field, Media in Focus¹⁰; Mark Ritson's columns in Marketing Week^12, 13.
• On IMC Report: brand equity, measuring effectiveness, the advertising primer, and the glossary entries for brand building and sales activation.