A 14-month Brainlabs study across 54 advertisers, published this week, shows organic search sessions falling 10.5% since AI Overviews scaled, while sessions from ChatGPT, Copilot, Gemini, and Perplexity climbed 163% and converted at 1.5x the rate of organic search. For small-business owners still reading their dashboards the old way, the volume signal and the value signal are now moving in opposite directions.

The dataset is unusually broad for agency-level reporting: 24 U.S. firms, 24 British brands, 6 in other markets, 19 sectors, 16 retailers, and 29 clients above 1,000 employees. Between January 2025 and April 2026, aggregate sessions across the roster dropped from 140.1 million to 125.4 million. Forty-six of the 54 clients saw a dip. Ahrefs has clocked individual sites losing as much as 58%.

The inflection, per Brainlabs senior SEO manager Sam Paez, was September 2025, when Overviews began appearing on at least 30% of U.S. results pages. After that threshold, organic sessions across the roster fell from roughly 20 million a month to under 15 million, while AI referrals climbed to about 200,000 monthly on average. Small in absolute terms. Different in behavior.

That behavioral gap is the story. AI-driven key events, purchases, sign-ups, meaningful engagement, rose 335% over the tracking window, and Paez notes some AI visits are miscounted as direct traffic when users open a new browser window. The traffic that survives is warmer, later in the funnel, pre-qualified by a chatbot that already summarized the category.

Sector distribution fits the theory. “Overwhelmingly, [Overviews] are being triggered by educational, informative discovery keywords. It is starting to trickle down to transactional, commercial [searches],” Paez said. Retail was largely spared: “Retail was one of the least affected by AI overviews, which makes sense with the AI overviews not triggering as much [against] transactional searches.” Fitness, fintech, insurance, and CPG absorbed the hit.

Sensor Tower puts ChatGPT at 1 billion monthly active users as of May 2026, with Claude at 56 million. The distribution surface is no longer hypothetical. Owners measuring only against a 10% session decline are reading a P&L with one column missing. “We need to start taking this channel seriously. It’s definitely a channel you should be including in your everyday measurement KPIs,” Paez said.

The paid side of the same shift is already arriving through Google’s AI Max rollout and ChatGPT’s imminent self-serve ad product. The open web isn’t ending. It’s being re-intermediated, and the new intermediaries send fewer clicks that mean more.

Sources