Google and AI Source Overlap Across 12 Medical Niches

A descriptive US-English benchmark of the overlap between explicitly exposed ChatGPT and Gemini citation sources and paired Google organic Top 20 results across 12 medical niches. The release contains 432 frozen questions, sector- and niche-level summary estimates, task-level URL and domain overlap metrics, ChatGPT-Gemini domain Jaccard results, top cited and matched domains, the full question and prompt manifest, a data dictionary, checksums, citation files, reusable figures, and an XLSX workbook. Fieldwork: August 7, 2026. Author: Evgeniy Yudin (Rotgar). Methodology reviewed by Boris Teplyakov, SEO Lead. The review covered methodology only and was not a medical subject-matter review of the questions, answers, or cited sources. This study measures descriptive source overlap only; it does not measure answer accuracy, source authority, rankings, traffic, leads, or patient outcomes. Canonical study: https://rotgar.com/medical/resources/google-top-20-chatgpt-gemini-source-overlap