Glossary
Market Share
Market Share is the percentage of total sales, revenue, or activity within a defined market that is captured by a specific company, brand, or product over a given period. In paid media and performance marketing, market share is measured through several lenses: impression share in Google Ads (the percentage of eligible impressions a campaign actually received), Auction Insights reports that reveal how often competitors appear alongside or above your ads, and share of voice metrics that quantify brand visibility across organic search, paid search, and social channels relative to competitors. Market share analysis informs budget allocation, bid strategy, and competitive positioning — losing impression share to budget constraints signals underinvestment, while losing to ad rank signals creative or quality issues that reduced bids cannot overcome. In programmatic advertising, market share data from DSPs and third-party measurement firms helps advertisers calibrate their share of total programmatic spend within a vertical. Market share is distinct from market size (the total opportunity) and market growth (the rate of expansion): a company can increase revenue while losing market share if the market is growing faster than the company. For performance marketers, market share is the strategic metric that connects tactical campaign KPIs (CTR, CPA, ROAS) to competitive outcomes — campaigns can be efficient on a unit basis while still ceding market position to competitors who are willing to accept lower near-term returns in exchange for share gains.