The first time someone explained share of voice to me, I thought it was just another vanity metric. You measure how much you're spending on advertising relative to your competitors, express it as a percentage, and then... what? But then I learned about the ESOV rule, and everything clicked. Share of voice isn't just a measurement of how loud you are. It's a predictor of future market share growth. That changes everything about how you should think about this metric.
Share of voice (SOV) measures a brand's visibility in the market as a percentage of total category activity, whether that activity is measured in ad spend, social media mentions, search visibility, or media coverage. According to Nielsen's 2025 analysis, SOV refers to a brand's media spending expressed as a percentage of all media expenditures in the category, in that market, on that channel, and at that particular point in time.
But the modern definition extends well beyond paid media. In 2026, share of voice encompasses paid, earned, owned, and shared media channels, making it a holistic measure of brand presence.
This is the part that turns SOV from an academic exercise into a strategic weapon.
Excess Share of Voice (ESOV) is the difference between your share of voice and your share of market. When SOV exceeds SOM (share of market), the brand tends to grow. When SOV falls below SOM, the brand tends to decline.
The most robust evidence for this comes from Binet and Field's analysis of the IPA Databank, which analyzed over 800 campaigns across decades of data. Their finding: a 10-point positive ESOV produces roughly 0.5 percentage points of market share growth per year.
Let me put that in practical terms:
| Brand's Market Share | Brand's Share of Voice | ESOV | Predicted Annual Market Share Change |
|---|---|---|---|
| 15% | 20% | +5 points | +0.25% growth |
| 15% | 15% | 0 points | Roughly stable |
| 15% | 10% | -5 points | -0.25% decline |
| 15% | 25% | +10 points | +0.5% growth |
This relationship has been called "the closest thing to a law of gravity that exists in marketing." According to Semetis's analysis of ESOV-driven growth, the rule holds across categories, geographies, and time periods, though the magnitude varies.
Modern marketers track SOV across multiple dimensions because brand visibility is no longer concentrated in a single channel.
The original and most traditional form. It measures your advertising spend as a percentage of total category ad spend. If the total category spends $100 million on advertising and your brand spends $15 million, your paid media SOV is 15%.
This remains the foundation for the ESOV calculation and connects directly to competitive parity budgeting decisions. The IPA research was primarily based on paid media SOV.
Your brand's share of mentions in news outlets, blogs, and editorial content. This is typically the domain of PR teams. A brand that generates significant press coverage can achieve high earned media SOV without proportional ad spend.
Your brand's share of social media conversations, mentions, and engagement within your category. According to Sprout Social's SOV measurement guide, social SOV is particularly valuable for brand awareness because it reflects real-time consumer conversations rather than just paid or algorithmic visibility.