MER

MER strips out platform-reported attribution entirely and instead compares total business revenue over a period to total ad spend over that same period, pulled straight from the bank account or order management system. This makes it immune to the inflated or deflated attribution that individual platforms like Meta can report, since Meta has no visibility into what a customer bought on another channel or in-store.

For agencies managing spend across multiple ad accounts and sometimes multiple platforms for one client, MER is the north-star efficiency number the client actually cares about, because it reflects real revenue, not modeled revenue. A client's finance team will reconcile against MER long before they trust a dashboard's ROAS column.