E-commerce
Marketing efficiency ratio (MER)
Total revenue divided by total marketing spend, across all channels; also called blended ROAS.
What it is
MER ignores attribution: it asks how revenue moves with spend in total, not which ad claims each sale.
Why it matters
For e-commercePlatforms each claim credit for the same orders. MER is the check that does not double count.
How it is measured
Formula
MER = total revenue / total marketing spendDivide revenue for a period by all marketing spend in that period, and watch the trend as spend changes.
A common mistake
Reading MER alone. It hides which channels work, so it pairs well with tests or modeling.