Excess share of voice

What it is

Share of voice, SOV, is a brand’s share of the advertising in its category. Share of market, SOM, is its share of the sales. Excess share of voice is the difference:

ESOV = SOV − SOM

A brand advertising in proportion to its size has an ESOV of zero. A brand advertising above its size has positive ESOV, and the evidence from decades of case data says its market share tends to grow, roughly in proportion. A brand advertising below its size tends to lose share, slowly at first.

Why it matters for a media plan

Most of a media plan is about efficiency: which channel, which week, which creative. ESOV is about the size of the pot. It answers the question that comes before allocation: is the brand spending enough, relative to its competitors, to hold or grow its position?

It also sets the split between brand building and activation. The long-run evidence puts the average optimum near 60:40 in favour of brand, with wide variation by category: closer to 50:50 for B2B and for online-transacted categories, higher for brand share in high-loyalty and subscription markets. A plan that is all activation can look efficient every quarter while the brand’s ESOV goes negative and its share follows a year later.

How it works

Compute both shares on the same basis and the same period, usually a year. Plot the category: every brand by share of market on one axis and share of voice on the other. The line where they are equal is the equilibrium. Brands above it are investing ahead of their size; brands below are coasting on it.

The planning use is to set a target ESOV and back out the budget. If the category spends X per year and the brand wants ten points of ESOV above its 15% share, its share of voice needs to be 25%, so its budget needs to be a quarter of X. Whether that buys the expected half point of share depends on the category, the creative and the channels, which is where the rest of the plan takes over.

Large brands enjoy a discount: they can hold share with slightly negative ESOV because of their existing salience. Small brands pay a premium: they need more ESOV per point of growth. Both effects are in the databank and both should be in the plan’s assumptions.

How Kuwalyst uses it

Benchmark-led plans in the Media Planner use ESOV as a sanity check on the brand budget before any allocation is made. Where competitive spend is available, the plan states the brand’s share of voice and share of market, its ESOV, and what the registry’s rule of thumb implies for share over the coming year, tagged as a benchmark. Where competitive spend is not available, the plan says so and proposes the source that would fill the gap.

The brand-versus-activation split starts from the registry entry for the category and is listed among the plan’s assumptions. The model, once fitted, tests it: brand channels with long carryover show up in the adstock and the baseline trend, and the plan can then say what the evidence, rather than the rule, supports.

Pitfalls

Different bases: share of voice on spend for one brand and on impressions for another is not a comparison. Fix the basis for the whole category.

Category boundaries: who is in the category decides every share. A narrow definition flatters the brand’s share of market and hides the competitors it is losing to.

The average is not your brand: half a point of share per ten points of ESOV is a category average across thousands of cases. Creative quality moves it by a factor of several. Treat it as a benchmark, tag it, and measure.

Confusing voice with attention: spend share on channels the audience ignores is not share of voice in any useful sense. The rule was built on media that delivered attention.