Why it matters
A buyer types "what does E7018 mean" and reads the AI Overview without clicking anything. Your welding distributor page may have supplied the spec that informed that answer, but you got no visit. That is a zero-click search. The reader has their answer, the sale conversation may still come, and your traffic logs show nothing. For industrial catalogs full of cross-reference lookups and spec questions, this is now the default path. The goal shifts. You want the citation, not the click, because being named as the source is what carries forward when the buyer is ready to act.
How to measure it
You cannot see a zero-click search in your own analytics, since no visit happens. Track it indirectly. Run your buyer prompts (cross-references, part-number lookups, "what is E7018") across engines and record whether your domain is cited in the answer, even when no click follows. Pair that with Google Search Console impressions on the same queries to estimate the gap between appearances and clicks.
In practice
Say a hydraulics distributor ranks a page explaining the difference between SAE and metric port threads. Pre-AI, that page earned a few hundred organic visits a month from buyers searching the comparison. Now an AI Overview answers the same question inline and clicks drop, but the overview cites the distributor's page as a source. The page stopped earning visits and started earning attribution. Treat that citation as the win and structure the page to keep earning it.