The excess share of voice calculator: are we spending like a brand that intends to grow?

Share of voice (SOV) is a brand's share of all advertising in its category; share of market (SOM) is its share of category sales. Excess share of voice (ESOV) is the difference, in percentage points. The calculator returns ESOV and the share growth per year that a widely quoted rule of thumb associates with it. The terms are in the glossary: share of voice and excess share of voice.

John Philip Jones argued in the Harvard Business Review in 1990 that a better guide to the budget than a fixed rate per unit sold was to compare a brand's share of market with its share of voice. He described brands whose voice is louder than their share as "investing", typical of new brands, and established brands that keep their voice below their share as "profit taking"¹. Les Binet and Peter Field later turned the relationship into a rule of thumb from IPA cases: on average, brands with positive ESOV tend to grow, by roughly half a point of market share a year for every ten points of excess share of voice². Their Effectiveness in Context showed how such rules vary with a brand's circumstances³.

The method has critics. An IPA essay calls ESOV a single-factor model applied to a multi-factor problem, and notes it is getting harder to calculate because reliable data on competitors' digital spend is scarce⁴. Mark Ritson has argued in Marketing Week that share of search should replace share of voice as the tracking measure⁵.

1. Share of voice your media spend (or impressions, or ratings) as a percentage of the category's, over a year. Note the source and what it misses, usually much of digital.
2. Share of market your sales as a percentage of category sales, by value or volume, for the same market and period.
3. Read ESOV and the expected growth as a sense check on ambition: is the plan spending like a brand that intends to grow?
4. Cross-check with share of search if spend data is weak⁵.

Illustrative figures; not benchmarks.

A brand with a 20% share of market and a 25% share of voice has ESOV of five points. The rule of thumb associates that with growth of about a quarter of a point of share a year, all else being equal. A new entrant with a 2% share of market and a 10% share of voice has ESOV of eight points: Jones would call it investing.

• Treating the result as a forecast It is an average relationship across cases, not a promise^2, 4.
• Mismatched markets or periods SOV and SOM must cover the same category, market and year.
• Ignoring digital spend you cannot see Note the gap rather than pretending the data is complete⁴.
• Spending to a decimal point Use ESOV to frame the ambition, then build the budget from objectives and tasks.

• Jones in the Harvard Business Review¹; the IPA on share of voice²; Effectiveness in Context³.
• The IPA's critique of ESOV⁴; Ritson on share of search⁵.
• On IMC Report: budgeting for IMC.