Marketing measurement has had four eras: panel-based (Nielsen, 1936–1995), digital-attribution (cookies and last-click, 1995–2023), MMM-revival (2018–2025), and causal-AI (2024–).
Three things converged 2022–25 to break the cookie-attribution stack: cookie deprecation, AI-driven creative volume, and AI-mediated discovery.
Working 2026 stack: MMM as truth-source, geo experiments as calibration, in-platform attribution as in-flight signal, citation share as the AI-mediated KPI.
The dashboards that look reassuringly precise are the ones that are lying. Honest causal measurement produces wide confidence intervals and the discipline is to make decisions inside that uncertainty.