Six academic studies that define how ChatGPT, Claude, Perplexity, Gemini, and Google AI Overviews cite the web. Authors named, methods explained, every number sourced. The reference document for practitioners, researchers, and journalists in AI visibility.
AI engines have replaced demographic audience segmentation. ChatGPT, Claude, Gemini, and Perplexity group buyers by the prompts they type — surfacing 14 primary consumer segments that are intent-shaped, not demographic.
The discovery layer has collapsed into five answer engines — ChatGPT, Claude, Gemini, Perplexity, and Google AI Overviews. Side-by-side data, citation behavior, and the linked playbook for each.
The University of Toronto's definitive audit of GPT-4o, Claude, Perplexity, and Gemini versus Google Search across 1,516 queries. Domain overlap, source typology, content freshness, and the controlled experiment on pre-training versus retrieval bias.
OpenAI Instant Checkout. Google Universal Commerce Protocol. Walmart as double anchor. The single shift that turns answer-engine visibility into a sales-channel revenue line.
ChatGPT, Claude, Perplexity, Gemini, and Google AI Overviews give five different answers to the same gambling query. The inconsistency is the story — for operators, regulators, and users.
Answer engines — ChatGPT, Claude, Gemini, Perplexity, Google AI Overviews — now answer most early-stage buyer research. The pillar on how they decide which brands get cited.
Citation Share is the headline metric of GEO — but a program with only Citation Share is a scorecard, not an operating system. The full seven-metric stack: Citation Share, Entity Authority, Retrieval Frequency, Prompt Coverage, Crawl Health, Cross-Engine Variance, Citation Decay Rate.
Citation Share is the share of AI-generated answers in which a brand appears. The KPI behind GEO, how it is measured, what it captures, what it does not, and how to set up a Citation Share program.
When a brand fixes its citation graph, the engines reflect it on staggered timelines: Perplexity in days, ChatGPT in days-to-weeks, AI Overviews in weeks, Gemini in weeks-to-months, Claude on the next training cycle. Wikipedia is the multiplier.