Excess share of voice (ESOV) is the difference between a brand’s share of voice and its share of market. If your advertising makes up 15% of all advertising in your category but you hold 10% of category sales, your ESOV is plus five points; if the numbers were the other way round, it would be minus five.
How excess share of voice works
Share of voice was originally measured as your share of total media spend in a category. Online, people now estimate it in several ways: your share of ad impressions, your share of branded searches, or your share of mentions on social media and in the press. Share of market is your slice of total category sales, by value or volume.
The calculation is a subtraction. Take a regional kitchen retailer with roughly 8% of sales across its area. If competitors together spend about £360,000 a year on advertising and the retailer spends £40,000, its share of voice is 10% of a £400,000 total, so its ESOV is plus two points.
The idea matters because of what it predicts. Working with the IPA Effectiveness Databank, the UK effectiveness researchers Les Binet and Peter Field found that brands which hold a share of voice above their share of market tend to gain share over time, while brands below it tend to lose share. Their often-quoted rule of thumb, set out in IPA publications such as Media in Focus (2017), is that ten points of ESOV goes with roughly half a point of extra market share growth a year, on average. That is an average across many brands and categories, not a promise for any single business. Binet later proposed share of search, a brand’s share of all branded searches in its category, as an early indicator of where market share is heading.
Why it matters for a UK business
ESOV gives you a reasoned way to set a marketing budget rather than copying last year’s figure. A challenger brand can work out how loud it needs to be to grow, and a market leader can see whether it is spending enough to defend its position. It also explains why cutting spend in a downturn can be costly: if rivals go quiet and you do not, your ESOV rises without any extra spend.
Small brands have an advantage here. Because their market share is small, a modest absolute budget can still put them ahead on voice within a niche or a region, for example within one county or one category of search terms.
Common mistakes
- Treating it as a guarantee. Weak creative, poor distribution or the wrong price will undo any amount of voice.
- Measuring voice on one channel only. Being loud on Google Ads while competitors dominate television, radio or social does not give you a real share of voice.
- Using it for short-term sales. The relationship shows up over a year or more, through mental availability, not in next week’s conversions.
- Guessing market share. A wild estimate of share makes the whole calculation meaningless.
How to act on it
Start with a sensible estimate of market share. For larger UK competitors, accounts filed at Companies House show turnover; small companies can choose not to file their profit and loss account, so their turnover is often missing. Trade bodies and industry reports can fill gaps.
Then estimate share of voice using what you can see. Google Ads Auction Insights shows your impression share against named competitors, keyword tools show branded search volume for each brand, and the Meta Ad Library shows which ads competitors are running, though not what they spend on ordinary ads.
Set a target ESOV for the year, plan spend to reach it, and track share of search monthly as your early signal. If you want help turning this into a budget and channel plan, that is part of my digital marketing strategy work.