Share of voice vs share of market: the rule that steers your brand budget

Many B2B companies decide their brand budget on gut feel. A round number, a percentage of revenue, or simply whatever is left after the performance campaigns. The problem: none of those methods tells you whether you invest enough to grow or so little that you lose ground. There is a better metric for that, and it hinges on the difference between share of voice and share of market. In this article you will learn what that difference means, why it steers your market share and how to use it as a budget model.

Share of voice vs share of market: what is the difference?

Share of market (SOM) is your share of your category’s revenue. If you sell 2 million in a market that turns over 20 million in total, your share of market is 10%. It is an outcome: a snapshot of where you stand today.

Share of voice (SOV) is your share of your market’s total media presence. If all players combined buy or earn 100 units of attention, and you account for 15 of those units, then your share of voice is 15%. It is an investment: a choice you make today about how much space you occupy in your buyers’ minds.

The crucial insight is that these two are not the same and are not meant to be the same. SOM looks backward at what you have sold. SOV looks forward at the attention you are building today. The difference between the two is not a measurement error, it is a control lever.

Excess share of voice: the growth rule

That difference has a name: excess share of voice, or ESOV. The formula is simple.

ESOV = share of voice minus share of market

If you advertise with a share of voice of 15% while your market share is 10%, you have a positive ESOV of 5 points. You take up more space than your current size justifies. If you advertise with 8% voice on a market share of 10%, you have a negative ESOV of 2 points. You are quieter than your size.

The underlying rule is one of the most broadly evidenced principles in marketing science, popularised by the work of Les Binet and Peter Field for the IPA. The core: brands with a positive ESOV win market share over time, brands with a negative ESOV lose it. Those who are structurally louder than their size grow. Those who are structurally quieter shrink slowly while no one notices.

That explains why market leaders are so hard to catch. Their market share lets them invest the most in absolute terms, while in relative terms they need to do less to hold their position. A challenger that genuinely wants to grow must deliberately buy more voice than its market share deserves. That feels uncomfortable, because you pay today for growth that only shows up later.

Why this is a budget decision model

This is where ESOV gets interesting. It is not a reporting figure you review after the fact, it is a model for setting your budget in advance. Instead of asking “how much can we spare?” you ask “how much voice do we need to move in the direction we want?”.

The reasoning goes like this. If you want to grow your market share, you need a positive ESOV. If you only want to defend it, an ESOV around zero is enough: a share of voice roughly in line with your market share. If you accept shrinking, for example because you are retreating to a niche, you can live with a negative ESOV. Your budget therefore follows from your ambition, not from whatever happened to be left over.

In concrete terms, you flip the calculation around. Estimate your market share. Determine which ESOV fits your growth goal. Add the two together to get a target value for share of voice. Then estimate what a share of that size costs in your category, based on what the market invests in total. That amount is your starting point, not the figure accounting suggests.

For a B2B SME, the challenge is that your SOV rarely runs entirely through paid media. Your voice also sits in content, in events, in the visibility of your people on LinkedIn and in earned mentions. That is good news: it means you can build a positive ESOV without a market leader’s media budgets, by being smart about where your voice comes from. It is exactly this kind of choice that a well-considered brand strategy underpins: not just what you say, but how much space you occupy and where.

The pitfalls when doing the maths

ESOV is a powerful model, but it is easily misapplied. Three pitfalls to avoid.

Share of voice is more than advertising. Anyone who equates SOV with media spend underestimates their own voice. Organic visibility, PR, content and the presence of your team all count. For B2B brands that live on expertise, earned voice is often the biggest lever.

ESOV buys direction, not a direct sale. A positive ESOV translates into market share growth over quarters and years, not into leads this week. Anyone who judges it on short-term numbers pulls the plug too early. This is long-term work that runs alongside your performance channels, not instead of them. How to make that longer payback period visible is something you can read in measuring the ROI of branding.

The input has to be right. Your market share and the total category investment are estimates. Be honest about that and use round, defensible figures rather than false precision. ESOV is a compass, not a calculator that is accurate to the decimal.

How to apply this in practice

Start small and honestly. Estimate your market share within a clearly defined market: a sector, a region, a product type. The sharper you define the market, the more usable the figure. An SME that takes “the entire B2B market” as its category ends up with a uselessly small market share. An SME that takes “accounting software for Flemish firms” gets a figure you can actually work with.

Then map your current voice across all your channels combined, and compare it with your market share. If you are below it, you know you are giving away ground today. If you are above it, you are investing in growth. That single insight is often enough to lift a budget discussion from gut feel to solid reasoning.

Building that lead is not a campaign but a process. A consistent voice that year after year exceeds your size builds brand equity that translates into preference, pricing power and a shorter sales cycle. That is the real outcome of a positive ESOV: not louder for the sake of being louder, but bigger because you buy today the space you fill tomorrow.

Want to back your brand budget with a model instead of a gut feeling? As a branding agency, we help B2B companies in the Benelux sharpen their share of voice and steer their investment toward growth rather than toward whatever happens to be left over. Get in touch and we will look together at where you stand today.