Paid Social in a Post-Cookie World: The Triangulation Playbook

Ask your ad platform for ROAS and it will happily oblige. Ask your P&L and you will get a different number. Ask an incrementality test and you may get a third. In a post-cookie world none of these views is wrong — each is partial. Mature teams stop picking one and start triangulating.

Three lenses, one truth

Platform data gives you speed and creative-level signal. Marketing mix modeling gives you budget-level truth, with a lag. Geo holdouts give you causal confidence on channels big enough to test. The playbook we run: platform data daily, MMM refreshed monthly, and a rolling calendar of holdout tests per major channel each quarter.

Making decisions when the lenses disagree

When the lenses conflict — and they will — the tie-breaker is margin, not attribution. We allocate budget against contribution margin estimates refreshed monthly, then let the next holdout adjudicate the argument. Teams that adopt this typically discover a fifth of their spend is non-incremental.

Reallocating that budget alone often funds the entire program. The goal is not perfect measurement — it is confident reallocation at speed.