Apps are not a prime conversion driver, so why in the world would Google optimize for that, if not to buff up CPMs?
Anonymous ad buyer
Three buyers told Adweek they saw between 33% and 90% of impressions in their Placement Reports, which Google rolled out in January 2022, were delivered to open web inventory, which buyers generally consider low quality.
However, Placement Reports are not reflective of an entire Pmax campaign since they don’t include search impressions. When buyers attempted to include Search impressions, the proportion of open web inventory was sometimes lower, though Google does not provide a full breakdown of all impressions by inventory type.
“Apps are not a prime conversion driver, so why in the world would Google optimize for that, if not to buff up CPMs and ensure delivery?” said another buyer, who declined to be named because they didn’t receive authorization from their agency. The buyer’s agency noticed Pmax inventory weighted more toward open web than it would prefer.
Other buyers told Adweek that overall Pmax performance is good enough and display inventory is sufficiently low such that they aren’t concerned.
“As long as the performance is decent, [the proportion of open web inventory] is kind of a meh issue,” said Adam Lovallo, vp at performance agency BMG360. “All display sucks, but it generally is only a small percent of spend, so we don’t mind. That said, we’d rather not buy display.”
A Google spokesperson said that wherever Pmax ads are delivered are the best places to meet advertisers’ goals.
“Performance Max optimizes for advertiser value based on their goals, not a specific percentage of inventory per channel,” a Google spokesperson told Adweek.
How to know where Pmax ads ran
The transparency of Pmax, while improving, is another frustration with the tool, buyers told Adweek.
Rigas and the first anonymous ad buyer understood Pmax inventory breakdowns by triangulating several different Google reports or by using third-party APIs, as all Pmax placement reporting for a campaign does not exist in one centralized place.
Advertisers can learn where the Pmax algorithm placed their campaigns via two reporting tools. According to the Google spokesperson, Placement Reports show the impressions that ran on open web inventory and Google’s owned & operated properties YouTube, Maps and Gmail, but critically not Google Search.
