The feeder strategy (PMax + Shopping)

Accounts running Performance Max and Standard Shopping together have a structural trap: PMax has priority in the auction, so left unmanaged it cannibalises the Shopping campaign that feeds it clean data. Budget Intelligence detects the hierarchy and manages it.

What it enforces

• The 20% rule - PMax's tROAS should be at least 1.20× Shopping's tROAS. The premium makes PMax selective, taking only the higher-value traffic and leaving Shopping its role.

• The spend split - a recommended 70-80% PMax / 20-30% Shopping balance.

• Cannibalisation flags - when the tROAS gap closes or inverts, the run flags it before Shopping quietly starves.

Example. Shopping runs at 3.5× tROAS and PMax at 3.6× - too close. The recommendation lifts PMax to at least 4.2× (3.5 × 1.20), restoring the hierarchy.

Good to know. If you've ever watched a Shopping campaign's volume drain away in the weeks after launching PMax, this is the mechanism - and the 20% rule is the fix.

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