What they did
Ahrefs compared organic click-through rates on search results with and without AI Overviews, across a sample of 300,000 queries. A later update to the study tracked the effect on position 1 specifically, measuring a 58% decline by December 2025.
How much weight to give it
Moderate, and it’s among the better AI Overview datasets available. The sample is large and the methodology is published, which is more than can be said for much of the commentary on this topic.
What it doesn’t prove
The core problem is selection. Google shows AI Overviews disproportionately on informational queries, and informational queries had lower CTR before AI Overviews existed. So part of the measured gap reflects which queries trigger a summary rather than the summary’s effect on behaviour. A clean answer would need the same queries measured with and without, which only Google can run.
Estimates across the published studies range from roughly 15% to over 60% depending on method and query mix. Any single figure quoted without its methodology should be treated as marketing. Our AI Overviews guide keeps the range rather than picking a favourite.