"Six ad units beat three, more inventory more money"

"Six ad units beat three, more inventory more money"

Fair: each additional unit is another impression, and up to a point total revenue does climb with unit count.

The asterisk is diminishing — and then negative — returns. Units four through six compete with one through three for the same advertiser budgets and the same viewport, so each new unit cannibalizes the auction value of the others.

🚩 Hidden variable: per-unit CPM decay. Going from three to six units often lifts impressions 100% while per-unit CPM drops 40%, netting a single-digit revenue gain — or a loss once the speed penalty cuts pageviews.

The real comparison is three well-placed units vs six crowded ones on revenue per session, not on impression count.

Not saying more units never help — saying counting inventory ignores that your own units bid against each other.