Why blended ROAS hides the real story in e-commerce accounts

Blended return on ad spend averages performance across every channel into one number, which is convenient for a summary slide and actively misleading for a budget decision, because it hides which specific channel is actually earning its allocation.

We routinely find accounts where one channel is performing well above target and another well below it, netting out to a blended figure that looks acceptable and hides an opportunity to reallocate a meaningful share of budget toward the better-performing channel.

The fix is straightforward in principle and rarely done in practice: report and make decisions at the channel level, and reserve the blended figure for board-level context only, never for channel-level budget calls.