What it means
Query share is the portion of total search demand for a topic that your site or page captures through its rankings. You take the queries that define a topic, weight them by search volume, and measure how much of that demand your rankings win. Kevin uses it as a proxy for topical authority: The more of a topic's queries you rank for, the more completely you cover it in Google's eyes.
Why it matters
Topical authority is hard to prove to a boss or a budget holder. Kevin built his measurement approach around that exact problem, quoting the reader whose boss keeps asking them to prove why topical authority is important and measure it. Query share turns an abstract claim about topical authority into a number you can track over time and benchmark against competitors on the same query set.
Say a mid-market B2B SaaS company defines its core topic with 400 queries worth 500,000 monthly searches combined. It holds top-10 rankings for queries representing 12% of that demand. After 6 months of filling entity and question gaps, its query share reaches 30%, and it uses that rise to justify continued content investment.
How to use this knowledge
Define a topic as a volume-weighted set of queries, then measure the share where you hold meaningful rankings and track that percentage over time. Benchmark your query share against competitors on the same set to see who actually owns the topic. Treat the queries you do not rank for as your content and internal-linking backlog, the same work that builds topical relevance.
Growth Memo guidance
Internal docs leaks and public signals from Google show that topical relevance, ie, how completely a site covers related entities and questions, is a real and important factor in ranking. — How to measure topical authority
Google rewards sites that cover a topic in-depth, and it does so by comparing how well the site covers relevant entities. — How to measure topical authority
Topical authority — the broader signal query share is meant to quantify.
Topical relevance — Google's term for how completely you cover a topic, which query share estimates.
Share of voice — the visibility metric query share adapts to a single topic's query set.
Content gap analysis — the method that turns unclaimed query share into a content backlog.