Attribute revenue to search by segmenting sessions that included at least one search and summing their revenue. On most sites, search touches a minority of sessions and a disproportionate share of revenue, because searching is an act of declared purchase intent.
Session-level attribution — did this converting session contain a search — is the honest version and the one to report. Last-click attribution to the search event understates search badly, because a shopper who searches, browses a category, then buys is credited entirely to the category page.
It counts only successful searches. The sessions where search failed and the visitor left are absent from the numerator and invisible in the report — so the measured contribution of search is always a floor, never a ceiling.
Track revenue per search session and per query. The head terms tell you what to merchandise by hand; the tail tells you what to fix systematically. Both convert an analytics number into a work queue.