Share of Voice (SOV)
A brand's relative share of promotional presence, detailing volume and spend, versus competitors in a category.
Share of Voice is a brand's share of total promotional activity within its therapeutic category relative to competitors, measured as detailing volume, promotional spend, or impressions depending on what data a brand can get. It's used as a proxy for how visible a brand actually is to prescribers, as distinct from how good its message is once an HCP is paying attention.
Commercial teams track SOV against market share over time because the relationship between the two is diagnostic. A brand gaining SOV without gaining share usually has a message problem, not a reach problem, and the fix belongs on the content side. A brand losing SOV while holding share is running lean, and the question becomes whether that's sustainable once a competitor spends up. Either way, SOV alone only answers how loud a brand is, not how good its message is.