Members on WebmasterWorld reported seeing significantly lower impression data (and thus lowered CTR, CPM and RPC reporting as well) since September 19th on their Yahoo Publisher Network stats. OvertureRep confirms that there was an error in their reporting, although all earnings and clicks stats were correct.
Today, we found an error in our YPN portal that caused inaccurate reporting of Ad Unit Impressions, CTR, CPM and Average RPC data for some of our publishers.
Number of clicks and Revenue reporting for all publishers is accurate and was not impacted by this error. We have issued a fix for this error and you will see accurate data going forward within the next 24 hrs.
So affected publishers should see their data updated within the next 24 hours with the correct impression stats.
Clarification: Older data will not be corrected but publishers will now see the correct data going forward.