We probed 47 categories with 1.2M queries across six engines. The result is a tight power law — and a per-category list of the sites that actually matter.
Common wisdom in GEO is that "authoritative sources" matter. We wanted to know which ones, in which categories, and by how much. Over Q1 2026 we ran 1.2 million simulated buyer queries across six major LLMs (ChatGPT, Perplexity, Gemini, Claude, Copilot, Google AI Overviews) covering 47 commercial categories. For every cited answer, we traced the underlying source. The finding is robust and uncomfortable: in any given category, fewer than 30 domains supply more than 60% of the LLM's information.
The map is uneven across categories. SaaS leans heavily on G2 and Capterra; healthcare on regulatory and clinical sources; CPG on review aggregators and lifestyle media; finance on a tight set of analyst sites. We publish the per-category top-10 source list, the methodology, and a public dataset for replication. The implications for content placement, source partnerships, and earned-media strategy are immediate — and uncomfortable for anyone still treating GEO as a content-volume game.