Why AdSense CPC plummeted this week

Alarm bells have been ringing for many AdSense publishers this week after CPCs dropped by up to 75% over the weekend. The unprecedented drops appeared to be hitting one traffic geo at a time, starting with the US and Canada on Saturday.

Although dramatic, the drops have not been universal. The drops were widely reported to be affecting AdWords impressions from particular Geos, but many publishers escaped untouched. In fact, despite widespread reports of the issue our sample across AdSense publishers who’s data we can access showed a slight aggregated increase at the weekend.

The good news for affected publishers is that the issue has now been resolved by Google, but this was a drop in earnings rather than a reporting problem. That means that the bad news is that many publishers will have earned less whilst affected.

Communication from Google about the issue hints at deliberate manipulation by some buyers:

Over the past 48 hours, a number of AdSense publishers alerted us to an issue with declining cost-per-click for ads on their sites. We were able to identify the cause of the issue quickly and resolve it quickly: Several ad buyers were using irresponsible campaign parameters, lowering query coverage for specific creative types in some countries. The ad buyers responsible have been blacklisted and impacted publishers should see that their coverage is back to normal in their AdSense account.

Quite what “irresponsible parameters” were used is unclear. There has not yet been any statement to offer re-assurance that this issue has been resolved in a way that would prevent other ad buyers having a similar negative impact in the future.