AI search and AI-generated overviews (AIOs) are reshaping how users discover content online – but how much do they really matter? At Coppett Hill, we’ve developed an AI Index, a structured framework designed to measure AI-driven traffic and give marketing teams a better understanding of how AI search impacts website visibility and engagement. Our AI Index covers a mix of B2B and B2C companies across multiple sectors, and covers two trends:

 

1. AI referral traffic from large language models (LLMs) to advertiser websites.

2. The presence of Google’s AI Overviews on the search results page for keywords which drive organic search traffic to advertiser websites.

 

What’s happening with LLM traffic to websites?

 

Since October 2024, our AI Index highlights a sharp increase in LLM-attributed traffic - particularly as a proportion of organic search within recent months, with the proportion growing by c.80% since the start of the year. While LLM-driven referrals are still a small proportion of overall traffic, their rapid growth suggests that marketing teams will need to rethink their organic strategies in the coming years.

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How are AI Overviews changing search behaviour?​

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To asses the impact of AI-generated search results, we've measured how often AIOs actually appear in search results for Google (by far the dominant search engine among our clients). Using the same mix of companies as in our AI referral analysis, we tracked the share of advertiser organic traffic exposed to these overviews.​

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Our tracker shows a sharp rise in AIO visibility, weighted by advertiser traffic (i.e. the search terms that matter most), from 6% in February to 25% in July. This is consistent with broader SERP analysis showing AIOs appeared in over a quarter of keywords across a sample of 1,000,000 SERPs, with both datasets pointing to a clear inflection point around Google's March Core Update - the same moment other SERP features, particularly featured snippets, saw sharp declines. 

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The highest AIO visibility in our tracker remains in sectors where users are typically seeking advice, explanations, or guidance - such as law firms and other professional services. Behavioural research supports this, showing that AI summaries are far more likely to appear for longer, question-based, or full-sentence queries. For example, only 8% of one- or two-word queries generated an AI summary, compared with 53% of 10+ word searches and 60% of queries beginning with a question word. However, we're also seeing growth across a broader mix of advertisers, including D2C retailers - indicating that AIOs are beginning to influence more of the funnel, not just informational, zero-click journeys but also searches with stronger signals of purchase intent. ​

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So, What Should You Do?​

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For most advertisers, there’s no immediate need to overhaul your search marketing strategy—yet. However, AI’s growing role in search means businesses should be proactive in understanding and adapting to these changes:

• Stay ahead by testing and adapting – Google remains the largest AI-powered marketing channel, and businesses need to treat it as an evolving space. Testing how AI-generated results affect search intent, rankings, and click-through rates is essential to understanding what drives visibility in this new landscape.

• Monitor LLMs’ role in your audience’s journey – Businesses need to track how their audience engages with LLMs and ensure their content remains visible in AI training data to maintain future discoverability.

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If you’d like to see how your business benchmarks within our AI trackers or discuss your company’s approach to AI disruption in search marketing, please contact us.   

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