Default 7-day-click attribution inflates reported ROAS by ~22%

Default 7-day-click attribution inflates reported ROAS by ~22%

Attribution window = how far back Meta credits a conversion to an ad. Default is 7-day-click + 1-day-view. ROAS = revenue ÷ ad spend.

Reported ROAS by window (same 35 accounts, identical spend):
— 7d-click / 1d-view: 3.4× (default)
— 1d-click: 2.6×
— GA4 last-click: 2.4×

The gap isn't error — it's Meta claiming sales that other channels also claim. Buyers who optimize to the 3.4× number overspend.

Fix: report on 7d-click for optimization (Meta needs signal), but judge profitability on 1d-click or a blended MER. Pick one truth source and hold it constant.

Read: the window you trust sets the budget you can survive — not the budget you wish you had.