Category Ownership Index (COI)
Also known as: COI, category ownership
The Category Ownership Index (COI) measures how thoroughly one brand dominates the buyer-intent questions of its category in AI recommendations, from 0 (absent) to 1 (owns every question).
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The Category Ownership Index (COI) measures how thoroughly one brand dominates the buyer-intent questions of its category in AI recommendations, on a 0 to 1 scale. It is computed by asking AI models brand-free category buying questions repeatedly and measuring which brand leads each answer. In the 2026 multi-industry study (3,750 responses, 250 questions, 5 industries, 3 models), EY owned consulting at 0.95, appearing as the lead recommendation in 47 of 50 consulting queries, while Stripe led fintech at 0.53 and HubSpot led SaaS at 0.38. The spread shows category structure: consulting behaves like a monopoly, SaaS like a contested market. COI pairs with the Competitive Vacuum Index (the share of questions no brand owns, 8% in the study) and the Displacement Score (how hard the incumbent is to unseat). The dataset behind the metric is open on Kaggle and Zenodo under CC-BY-4.0.
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Our Category Ownership Index: The Open Dataset research found: EY owns consulting at 0.95 COI; 8% of questions are vacuums
Read the full researchFrequently asked questions
How do I find my brand's COI?
If your brand is one of the 50 in the public study, your profile at open.rankfor.ai/brands shows the queries you own, where you are strong, and where you are absent. For any other brand or category, the same protocol runs on the platform: brand-free category questions, repeated, across models.
Does a low COI mean my brand is losing?
A low COI in a category with a moderate Gini means the field is contested and open: the study found mean concentration of 0.284 and true dominance above 3:1 to be exceptional. The cheapest wins are the competitive vacuums, the 8% of questions AI answers with no established brand at all.
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