MER is total revenue divided by total marketing spend across all channels — the blended, attribution-free sanity check on whether marketing overall is paying for itself.
Definition
Unlike ROAS, MER doesn't try to credit individual channels; it takes all revenue over all paid spend for a period. That makes it immune to attribution disputes and double-counting — every platform can claim the same conversion, but MER only counts it once. Its weakness is the inverse: it can't tell you which channel to cut or scale, only whether the whole is healthy.
Why it matters
When platform-reported ROAS looks great everywhere but MER is sliding, platforms are taking credit for revenue that would have happened anyway. MER is the tripwire that catches attribution inflation — which is why DTC finance teams increasingly manage to it.
In agentic execution
Agentic execution needs an honest scoreboard: Adlyse's cross-platform view lets teams set channel-level targets that reconcile with blended reality, and agents execute reallocations against that fuller picture with human approval.
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