The short version

Catherine Perloff predicted on January 9, 2026: “Open-web programmatic CPMs will continue to compress in Q1 2026 as walled-garden retail media siphons budgets, with at least one major SSP issuing a guidance cut.” Verdict: Called it. Magnite cut Q1 2026 revenue guidance citing exactly this dynamic; PubMatic followed with softer language. Open-web CPM index from Operative was down 9% YoY…

Prediction by

Catherine Perloff

On January 9, 2026

“Open-web programmatic CPMs will continue to compress in Q1 2026 as walled-garden retail media siphons budgets, with at least one major SSP issuing a guidance cut.”

Follow-up

Magnite cut Q1 2026 revenue guidance citing exactly this dynamic; PubMatic followed with softer language. Open-web CPM index from Operative was down 9% YoY in March.

From the High Caliber AI network — see the AI for PR module in the course.