The great decoupling is the widening gap between how often a site's pages are shown in search (impressions) and how often they are clicked (clicks and click-through rate). Impressions stay flat or climb while clicks fall, so the two lines that used to move together pull apart.
The cause is answers moving onto the results page. When an AI Overview or a featured snippet resolves the query in place, the searcher is satisfied without a visit, the zero-click pattern. Your page still earns the impression for being displayed inside or beside the answer, but the click becomes optional. Ahrefs measured the effect on informational queries at an isolated top-result click-through-rate drop of roughly 34.5% (March 2025 data) rising to up to 58% in its 2026 update, single-vendor and Google-AI-Overviews-specific, so directional.
The decoupling reframes what to measure: falling clicks against steady impressions is not necessarily lost visibility. It often means you are being shown and read inside answers. It is distinct from rank-decoupling (a page no longer needing a top-10 rank to be cited). The durable scorecard becomes whether you are cited inside the answer, not clicks alone.