MER vs ROAS: the measurement framework that scales businesses.
MER (Media Efficiency Ratio) = total revenue / total ad spend across all channels for a given period. It is the simplest, most resistant-to-gaming, and most operator-friendly performance metric. CFOs intuitively grasp it. Founders can defend it in board meetings. It cannot be inflated by attribution windows.
We model MER in two layers: blended MER (the whole business) and incremental MER per channel (the lift each channel produces above baseline). Incremental MER is the harder number — it requires hold-out tests, geo experiments, or full MMM to estimate properly — but it is the number that tells you whether to scale a channel or pull back. The brands operating on incremental MER are making 5–10× better budget decisions than the brands still optimising to platform ROAS.