Shifting budget off weekends saved 18% on CPM

Shifting budget off weekends saved 18% on CPM
Electronics retailer, 56d, $190k spend, dayparting test.

Weekend CPMs ran consistently hotter as more advertisers competed for the same impressions.

CPM by daypart:
— Sat–Sun: $31
— Tue–Thu: $25 ▼18%

Reweighting 40% of budget from weekends into the Tue–Thu trough, with no change to total spend, dropped blended CPA from $40 to $35 ▼13%. CVR held — these weren't worse buyers, just cheaper impressions.

Read: CPM isn't fixed. Audit your day-of-week curve before you accept the account's blended cost.