How do small mobile game teams diagnose ad revenue drops?

I’m trying to organize a practical way for small mobile game or app teams to think about ad revenue drops.

For bigger studios, there may be someone dedicated to analytics, monetization, dashboards, and weekly reporting. But for a small team or solo developer, the question is usually much simpler:

Revenue changed. What should I check first?

My current thinking is that “eCPM dropped” is often too broad as a first explanation.

A revenue drop could come from several different places:

• impressions changed

• fill rate / match rate changed

• eCPM changed

• country mix changed

• one placement stopped showing as often

• one ad source or mediation source stopped filling

• a product update changed traffic or session behavior

For example:

If revenue drops but eCPM is stable, it may not be a pricing problem. It could be traffic, fill, placement exposure, or country mix.

If impressions and fill are stable but eCPM drops, then pricing, demand, country mix, or ad source performance may be more likely.

For small teams, I wonder if the useful habit is not building a complex analytics process, but having a simple weekly review order:

1. Did impressions change?

2. Did fill rate change?

3. Did country mix change?

4. Did one placement change?

5. Did one ad source change?

6. Did eCPM actually change?

I’m curious how other developers think about this.

If you monetize a mobile game with ads, what do you usually check first when revenue changes?

Do you look at eCPM first, or do you split the problem by traffic, fill, country, placement, and ad source?