Averages hide the problem

A campaign converting at an acceptable aggregate rate can easily contain one source converting well above it and two converting at close to zero. The average looks fine. The buyer is still paying for the two.

Because the aggregate is stable, nobody investigates until the mix shifts and the average falls. By then the underperforming sources have been running for weeks.

The conversation it enables

When both sides can see performance by source, the discussion stops being about whether quality is good and becomes about which specific source to pause. That is a question with an answer, and it can be actioned the same day.

It also protects the publisher side. A single bad source dragging an average down would otherwise result in the whole partnership being questioned, when the correct action is much narrower.

Acting on it quickly is the whole point

Reporting that arrives monthly allows a bad source to run for a month. The value is in the speed of the response, not the existence of the report.

Same-day action on a clearly underperforming source costs very little and prevents the slow erosion that ends most buying relationships in this industry.