Confirmed: adding 3 creative sizes raised fill 6%

Confirmed: adding 3 creative sizes raised fill 6%
A publisher only accepted 300x250 and 728x90. Demand existed for sizes they blocked.
— Added 320x100, 300x600, and native to their ad units
— Updated line item size mappings in GAM
— 300x600 alone cleared at a 40% CPM premium over 300x250
Overall fill rose 6% and average display CPM climbed because higher-value formats finally had inventory to buy.
Impact: Every blocked size is demand you're refusing. Open the format list.
Confidence: sourced