Iain Harper's Blog

For two weeks in January 2026, a browser extension removed AI Overviews from the Google search results of 374 people. The remaining links moved silently up to fill the gap, so the interface looked just as the search always had. At the end of the two weeks, researchers asked participants how they felt about their search experience: satisfaction, quality, and ease of finding information. On every measure, the numbers matched the group that kept their overviews. Nobody missed them. The only difference was that people without overviews left Google for other sites 67% more often.

This field experiment by Saharsh Agarwal of the Indian School of Business and Ananya Sen of Carnegie Mellon, published on SSRN in April and revised in June 2026, produced the first causal measure of what Google's AI Overviews are costing the rest of the web. The answer is 40% of outbound organic clicks on queries where overviews appear, with no measurable benefit for the people doing the searching. On 20 May, at Google I/O, the company made AI Mode, that demonstrably made no improvement to the user experience, the default search experience worldwide.

What the experiment measured

The study recruited 1,065 US desktop Chrome users through Prolific and randomly assigned them to one of three groups. A control group saw Google as normal. A treatment group had AI Overviews removed in real time by the extension whenever they would otherwise have appeared, with organic results shifting up to fill the gap so cleanly that over 95% of participants reported noticing nothing. A third group was redirected into Google's AI Mode for all queries.

The experiment design settles a methodological argument that has run since the first observational studies appeared. Ahrefs, Pew Research, and Similarweb all pointed at the same traffic decline, but none could prove that the overviews caused it rather than some other change in search behaviour or Google's algorithm. Agarwal and Sen's extension created the counterfactual that observational data cannot. The only systematic difference between the two primary groups was whether the overview appeared. Everything else–the queries, the organic results, the ads–was the same search engine on the same day.

The numbers were stark. For queries where an overview appeared (about 41% of all searches), hiding it increased outbound organic clicks from 0.37 to 0.62 per search. Sponsored clicks stayed at 0.02 in both groups. Total search volume did not change. The overview did not create anything; it simply kept the 40% of clicks it absorbed inside Google.

After the main two weeks, the researchers swapped the conditions. The group that had been browsing without overviews got them back, and their outbound clicks fell from 0.61 to 0.33 per search. The group that had been seeing overviews lost them, and their clicks rose from 0.33 to 0.55. Same people, opposite intervention, mirror-image result.

The “higher-quality clicks” defence

Google's vice president of product for Search, Liz Reid, has characterised AI Overview clicks as “higher-quality clicks” that signal stronger purchase intent and longer downstream engagement. In April 2026, the company advanced a “bounce clicks” explanation, arguing that overviews mainly remove low-value visits — the kind where a user lands, finds nothing useful, and taps the back button within a few seconds.

Agarwal and Sen tested that claim directly. For every click that reached a downstream website, they measured whether the user bounced (left within ten seconds with no further navigation), how long they stayed on the page, and whether they hit the back button to return to search. Across all three measures, there was no difference between the group with overviews and the group without. The extra clicks generated by removing overviews were no different in quality from the clicks Google's system allowed through. The authors are careful to note that Google may measure something further down the funnel that the extension cannot observe. But at the top of the funnel, where the “higher-quality” claim was made, nothing supports it.

In contrast, Adobe Digital Insights' Q1 2026 analysis found that visitors arriving from AI assistants converted 42% better than non-AI traffic, reversing March 2025, when the same channel converted 38% worse. The volume is small, roughly 1% of total site traffic for most businesses, but the quality gap matters for anyone trying to value what remains.

Although the findings appear contradictory, They measure different things, so both can be true. Agarwal and Sen answered: does the AI overview filter out only the junk clicks? No. The clicks it suppressed were the same quality as the ones that got through. It just reduced volume.

Adobe looked wider but shallower. They took all traffic across thousands of sites and split it two ways: came from an AI assistant, or didn’t. Then compared conversion rates. That’s broad, but it can’t answer the Google question, because “AI assistant traffic” doesn’t isolate Google’s overview clicks. Those just get lumped into ordinary search traffic. So Adobe tells you assistant referrals convert well; it tells you nothing about whether Google’s surviving clicks are any good. Agarwal and Sen looked only at Google: narrow but deep: one channel, controlled comparison, cause and effect.

The mechanism, however, is straightforward: the AI overview wins the way anything wins in position zero. In the study, 87% of AI Overviews appeared above all organic results. When the overview sat at the top, removing it led to an 88% increase in outbound clicks. When it appeared lower on the page, the effect disappeared. People did not seek out the overview. They consumed whatever occupied the prime on-page real estate, the way supermarket shoppers take whatever sits at eye level on the shelf. Move the product, and the behaviour reverses instantly.

Forced into Google's fully conversational search interface, users rated their satisfaction at 2.9 out of 5, compared with 4.0 for both other groups. Attrition was roughly four times higher. Some participants installed workaround extensions to escape. This is the experience Google chose, on 20 May, to make the global default. Record queries and accelerating search revenue explain the decision. The fact that their own experiment's closest analogue produced the lowest satisfaction scores and the highest quit rates does not seem to have figured in the calculus.

Meanwhile, roughly twenty national news outlets are negotiating licensing deals for the privilege of appearing in these overviews, with Google winding down its older news-payment programme and making future payments conditional on granting AI training rights. If you are not one of those twenty, nobody is coming to the table. The response has to be self-directed.

Read your own exposure

Not all traffic is equally at risk. Agarwal and Sen classified queries into informational, navigational, and transactional categories. Informational queries accounted for 71% of all searches in the study and had a 53% AI Overview trigger rate. This is where the entire effect played out. Navigational searches (someone typing a brand name to find the website) triggered overviews in only 6% of queries, and transactional searches (purchase-intent, booking, downloading) in 15%. Neither category showed a statistically meaningful decline in clicks.

This means that if your search traffic comes through “what is” and “how to” queries, you are sitting ducks. If it comes from people searching for your name or your products by name, the damage is minor and may stay that way. Open your Search Console, filter for query type, and look at the split. The ratio between informational and branded traffic is the single best predictor of how badly this will hurt.

For many smaller businesses, an audit will show that informational traffic was always the least valuable, even though it has traditionally been encouraged to build domain authority. A plumber whose search visibility comes from “how to fix a leaking tap” was getting visits from people actively trying not to hire a plumber. That traffic was always thin on conversions, and the overview is now absorbing exactly those clicks. The branded traffic, from someone searching for the plumber by name after a recommendation, was always the higher-value stream, and it remains largely untouched.

Stop producing what the machine can summarise

The clicks that persist in a world of overviews share a common trait: the user wanted something the summary could not provide. A named opinion. A tool. A dataset. An experience report. This matches the evidence from the GEO literature I have previously reviewed. The Princeton benchmark found that content with sourced statistics, named quotations, and inline citations earned more citations from AI systems. ZipTie's cross-platform analysis found that sites with high original-data density received 4.3 times more citation occurrences per URL than directory-style listings. The surviving trickle rewards specificity. What a summary can reproduce, the summary will absorb. What it cannot reproduce, because it requires a person to have done, measured, or decided something, retains its click.

For a smaller business, this completely changes the question of content. The commodity “what is X” post, the 1,200-word explainer written to capture an informational keyword, was always a bet on Google continuing to send traffic to the answer. This content type has taken a 40% haircut and already converted poorly. That is a signal to stop producing it, or at least to stop treating it as a customer acquisition channel. Spend that same effort on content the summary cannot assimilate. Publish your own data, even if the dataset is small. Name your prices, your methods, your results, your opinions. Write the thing only you could write because only you did the work, and leave the commodity answer for the overview. Fix your GA4 attribution before drawing conclusions. AI referral traffic typically defaults into “Direct” or “Referral” buckets, and only 14% of marketers track it as a separate channel. You cannot manage what you have filed under miscellaneous.

Build the channels the intermediary cannot close

One result in the study was completely unaffected by the presence or absence of overviews: ad clicks. Free organic traffic from search fell 40%. Paid traffic held steady. If your free visitors from Google are disappearing, the route Google left open is the one you pay for, and that was clearly not an accident. If you start to spend more on Google Ads to replace the traffic it used to send for free, it should be watched closely for true return on investment.

So what should be done? Google has remained an intermediary for organic search traffic long after others cut it off at the knees to drive ad revenue. But the organic game has become increasingly difficult as ad slots and other additions to the search engine results page have made the real organic links less and less obvious. The direction of travel has been clear for many years.

Relying on an intermediary’s whims for traffic, even one as durable as Google, has always been a Hobson’s Choice. As its presence continues to fade, we return to basics: email lists, direct bookmarks, repeat visits, communities, and all the channels that do not pass through a search results page.

None of this is new advice; the case for greater focus on owned channels has been made for a decade, and each year the argument grew stronger and the urgency louder while the execution stayed more or less the same. The difference now is that experimental evidence puts a number on the cost. Every month that informational traffic goes unprotected by a direct relationship is another month in which 40% of those visits vanish into a summary.

One caveat deserves emphasis. Do not block AI crawlers outright. The major labs have split their bots into training crawlers and search crawlers. OpenAI separated GPTBot from OAI-SearchBot in late 2024, and Anthropic made the same split with ClaudeBot and Claude-SearchBot. Blocking the training crawler is your call. Blocking the search crawler cuts you out of the AI answers that are replacing the links you used to get. A Rutgers and Wharton study published in December 2025 found that publishers who blocked AI bots across the board experienced a 23% traffic decline compared with peers who allowed crawling. Google is the harder case, because Googlebot still handles both search indexing and AI features in a single crawler, which is exactly the bundling the CMA’s conduct requirements are trying to force apart.

The empty space

The 374 participants whose overviews were silently removed are, as far as the published literature shows, the only group of people to have experienced modern Google search without AI-generated summaries and been formally asked what they thought. They reported feeling no difference whatsoever.

That absence is visible only from the other side of the results page, where a company watches the traffic graph flatten and wonders whether visitors are finding better answers or simply never leaving the search process. Agarwal and Sen's contribution is to show that the latter is the case. The visitors are not finding better answers; they are milling around in the foyer before going home.

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