The GEO Brand Citation Index is a monthly open research dataset tracking how frequently brands are cited by major AI systems — ChatGPT, Perplexity, and Gemini — in response to common tool evaluation queries. This release covers March 2026 and includes 41 brand-level observations across three verticals: SEO & Marketing, CRM & Sales, and AI & LLM Tools. Methodology: Each brand is queried across standardised prompts on ChatGPT (GPT-4), Perplexity AI, and Google Gemini. Citation frequency is normalised to a 0–100 scale relative to the most-cited brand in each vertical per platform. The Delta metric captures the gap between ChatGPT citations (reflecting training data prominence) and Perplexity citations (reflecting live web visibility), surfacing which brands have current web presence versus historical AI memory only. Archetype Classification: Dominant: Cited consistently across all three platforms - AI Memory: High ChatGPT citations, low Perplexity (training data only) - Live Search: High Perplexity citations, lower ChatGPT (current but not deeply embedded in training data) - Consensus GEO: Balanced moderate citations across all platforms - Ghost: Cited historically but near-absent in live AI responses - Unclassified: Insufficient citation volume for archetype assignment Dataset columns: Month, Brand, Vertical, ChatGPT_Citations, Perplexity_Citations, Gemini_Citations, Delta, Archetype Live tool and full methodology: https://thegeolab.net/geo-brand-citation-index/