No, we can’t say Facebook CPMs are up because of the News Feed change

No, we can’t say Facebook CPMs are up because of the News Feed change 800 450 C-Suite Network

It’s a frustrating truth: Sometimes a data set just can’t tell the story you want or think you should be hearing.

On Thursday, a story in Recode relied on new data to suggest that Facebook’s change to its News Feed to de-emphasize commercial posts in favor of those by individuals may indeed be causing people to spend less time on the social network — just as CEO Mark Zuckerberg had said could happen when he announced the coming rollout on January 11.

The canary in the coal mine? Shrinking ad impression growth and rising growth in cost for those impressions since the change in January and February. The story was picked up by multiple outlets.

The conclusions

The data showing changes in CPMs (the average cost per 1,000 ad impressions) and impressions in January and February come from a data set shared by AdStage, a cross-channel campaign reporting and automation platform and Facebook marketing partner.

From the Recode story:

The general thinking is that less time spent on Facebook typically equates to fewer ads seen on Facebook.

That seems to be the case, at least based on early data. The number of ad impressions Facebook delivered in News Feed in January was down year over year, and in February ad impressions were up, but at a much smaller rate than previous months


Facebook CPMs — the cost of a thousand ad impressions — was up 122 percent year over year. In February, CPMs were up 77 percent. It marked the two highest year-over-year jumps in ad prices for Facebook over the past 14 months.

So, impressions went down in January and back up in February compared to the previous year. And CPM growth spiked in January and remained high in February compared to 2017.

I asked AdStage if they’d share their data with me. They did.

The problems & more data

Looking at the data, I cannot see how it can tell a correlation-causation story that falling impressions and rising CPMs are signals that people are spending less time on Facebook. Maybe the News Feed change is causing people to spend less time on Facebook. Maybe it isn’t. But this data doesn’t help us figure that out.

There’s also a timing issue. The change was announced almost halfway through January and wasn’t fully rolled out yet. Wouldn’t we see more impact in February than in January?

Making some kind of early verdict on the News Feed change was also not AdStage’s intention with this data. The company understands it represents a relatively small segment of advertisers and ad dollars running through Facebook, and there are lots of caveats and other signals that can’t be parsed out to draw that kind of conclusion.

Furthermore, the impression and CPM changes are part of a trend, as the Recode piece acknowledges: “The algorithm change may just be exaggerating a trend we were already seeing.” Maybe the algorithm is exaggerating a trend, maybe not. This data can’t answer that one way or the other.

Here are the impression and CPM growth trend charts from AdStage:

Source: AdStage, Facebook News Feed ads only
Source: AdStage, Facebook News Feed ads only

You’ll likely notice that the…