How to read a revenue report without fooling yourself

Most revenue arguments are really unit-of-measurement arguments. Two people look at the same week and disagree because one is reading page RPM and the other is reading session RPM.

Pick the denominator deliberately

• Page RPM tells you how well a single pageview monetises. It moves when your layout or floors change.
• Session RPM tells you how well a visitor monetises. It moves when your traffic mix or pages-per-session changes.
• Impression CPM tells you what buyers pay. It moves with demand, seasonality and your floors.

A layout change that adds a slot will usually lift page RPM and can still lower session RPM if it costs you a pageview. Only one of those numbers reflects the business.

Always segment before concluding

Aggregate RPM is a weighted average of very different traffic. A 10% drop is frequently just a shift in geo mix — more Tier-3 traffic from a viral post — with every individual segment flat or up. Segment by geo, device and traffic source before you change anything.

Seasonality is not a mystery

Q4 CPMs are 30–60% above the annual average and January is always brutal. Compare to the same period last year, not to last month, and you will make far fewer panicked decisions.

The most expensive optimisation is the one made in response to normal variance.