What they did
Ahrefs put 15,000 long-tail questions to Google, Bing and four AI assistants (ChatGPT, Gemini, Copilot, Perplexity), then checked whether the pages the assistants cited also ranked in Google.
What they found
On average only 11.9% of the pages cited by AI assistants ranked in Google's top 10 for the same question. About 80% of cited pages did not rank anywhere in Google for that query. Perplexity aligned most closely at 28.6%, while ChatGPT, Gemini and Copilot each sat near 8%.
How much weight to give it
It compares several assistants on the same question set, which makes the cross-engine gap meaningful. The finding that AI retrieval barely tracks Google rankings is well supported here.
What it doesn't prove
Long-tail questions only, one vendor, and an August 2025 snapshot. AI assistants rewire their retrieval frequently, so the overlap figure is a moving target.