Study: People Use Google and AI Assistants Together
Similarweb found that 95% of ChatGPT users also appear in Google's audience, a share that held steady from September 2025 through May 2026 even as visits to generative AI platforms grew 70% year over year. The firm reads the overlap as AI being added to search rather than replacing it.
A Bocconi University working paper points the other way on a different measure. Using Comscore desktop clickstream data from October 2024 to July 2025, it found households that gained access to ChatGPT Search cut traditional search queries by 3.14 per week, about 9.4% below the pre-expansion average of 33.51, with the decline reaching 17.0% after 20 weeks. Referrals to academic sites fell 32.8%, reference sites 26.5%, developer sites 15.1% and news sites 13.4%, while marketplaces and entertainment barely moved.
Both can be true because overlap counts people and the Bocconi study counts queries per household. Similarweb's report does not measure query-level substitution and excludes API usage, desktop apps and in-app AI features, which the firm says are more likely to replace search activity than add to it.
A separate field experiment published on arXiv on August 18 put 1,100 US Chrome users into standard Google, Google with AI Overviews hidden, or Google with all searches routed through AI Mode. In the AI Mode group, click-through to external sites fell 18.8 percentage points and sessions dropped by about 0.92 per day from an average of 4.0, with heavier Google users seeing the larger decline. For brands tracking referrals, the three measures of people, queries and clicks can move independently.
Reported by Search Engine Journal ↗
Topics: Google Search, ChatGPT, Measurement